Method for transmitting appropriate meta data to display device according to transmission protocol version

ABSTRACT

A transmitting method according to one aspect of the present disclosure is a transmitting method of a playback device, and includes: when a version of a transmission protocol is a first version, transmitting first meta data to a display device without transmitting second meta data to the display device, the transmission protocol being used to transmit a signal between the playback device and the display device, the first meta data including information that is commonly used for a plurality of images included in a continuous playback unit of a first video signal and relates to a luminance range of the first video signal, and the second meta data including information that is commonly used for a unit subdivided compared to the continuous playback unit of the first video signal and relates to the luminance range of the first video signal; and when the version of the transmission protocol is a second version, transmitting the first meta data and the second meta data to the display device.

BACKGROUND

1. Technical Field

The present disclosure relates to a transmitting method, a playbackmethod and a playback device.

2. Description of the Related Art

Conventionally, image signal processing devices which improve luminancelevels which can be displayed are disclosed (see, for example,Unexamined Japanese Patent Publication No. 2008-167418).

SUMMARY

In one general aspect, the techniques disclosed here feature a methodused by a playback device, including: when a version of a transmissionprotocol is a first version, transmitting first meta data to a displaydevice without transmitting second meta data to the display device, thetransmission protocol being used to transmit a signal between theplayback device and the display device, the first meta data includinginformation that is commonly used for a plurality of images included ina continuous playback unit of a first video signal and relates to aluminance range of the first video signal, the second meta dataincluding information that is commonly used for a unit subdividedcompared to the continuous playback unit of the first video signal andrelates to the luminance range of the first video signal; and when theversion of the transmission protocol is a second version, transmittingthe first meta data and the second meta data to the display device.

Additional benefits and advantages of the disclosed embodiments willbecome apparent from the specification and drawings. The benefits and/oradvantages may be individually obtained by the various embodiments andfeatures of the specification and drawings, which need not all beprovided in order to obtain one or more of such benefits and/oradvantages.

It should be noted that general or specific embodiments may beimplemented as a system, a method, an integrated circuit, a computerprogram, a storage medium, or any selective combination thereof.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a view for explaining development of a video technology;

FIG. 2 is a view for explaining an HDR (High-dynamic-range imaging)position;

FIG. 3 is a view illustrating an image example indicating an HDR effect;

FIG. 4 is a view for explaining a relationship between masters,distribution methods and display devices in case of introduction of theHDR;

FIG. 5 is an explanatory view of a method for determining a code valueof a luminance signal to be stored in content, and a process forrestoring a luminance value from a code value during playback;

FIG. 6 is a view illustrating an example indicating HDR meta data;

FIG. 7 is a view illustrating a storage example of static HDR meta data;

FIG. 8 is a view illustrating a storage example of dynamic HDR metadata;

FIG. 9 is a view illustrating a storage example of dynamic HDR metadata;

FIG. 10 is a flowchart of a method for transmitting static HDR metadata;

FIG. 11 is a flowchart of a method for processing HDR meta data;

FIG. 12 is a block diagram illustrating a configuration of a data outputdevice;

FIG. 13 is a view illustrating a data structure example of a SEI(Supplemental Enhancement Information) message in which HDR meta data isstored;

FIG. 14 is a view illustrating a data structure example of a SEI messagein which HDR meta data is stored;

FIG. 15 is a view illustrating a data structure example of a SEI messagein which HDR meta data is stored;

FIG. 16 is a block diagram illustrating a configuration example of adata output device;

FIG. 17 is a block diagram illustrating a configuration example of a DR(Dynamic Range) converter;

FIG. 18 is a block diagram illustrating a configuration example of theDR converter;

FIG. 19 is a view illustrating an example of instruction contents of anHDR meta interpreter;

FIG. 20 is a view illustrating an example of instruction contents of theHDR meta interpreter;

FIG. 21 is a view illustrating an example of instruction contents of theHDR meta interpreter;

FIG. 22 is a block diagram illustrating a configuration example of thedata output device;

FIG. 23 is a view illustrating a combination example of characteristicsof a video signal and the display device, and an output signal of thedata output device;

FIG. 24 is a view illustrating an example of an operation model ofplaying back various signals and outputting the signals to various TVs;

FIG. 25 is a view illustrating a storage example of static HDR meta dataand dynamic HDR meta data;

FIG. 26 is a view illustrating an example of a method for displaying auser guidance;

FIG. 27 is a view illustrating an example of the method for displayingthe user guidance;

FIG. 28 is a view illustrating an example of the method for displayingthe user guidance;

FIG. 29 is a view illustrating an example of the method for displayingthe user guidance;

FIG. 30 is a flowchart of a method for transmitting dynamic HDR metadata which depends on a HDMI (High-Definition Multimedia Interface)(registered trademark and the same applies likewise below) version;

FIG. 31 is a flowchart of a method for transmitting static HDR meta datawhich depends on a HDMI version;

FIG. 32 is a flowchart of a method for controlling a luminance valueduring playback of an HDR signal;

FIG. 33 is a view for explaining a dual disk playback operation;

FIG. 34A is a view illustrating an example of a display process ofconverting an HDR signal in an HDR TV and displaying an HDR;

FIG. 34B is a view illustrating an example of a display process ofdisplaying an HDR by using an HDR supporting playback device and an SDR(Standard Dynamic Range) TV;

FIG. 34C is a view illustrating an example of a display process ofdisplaying an HDR by using an HDR supporting playback device and an SDRTV which are connected to each other via a standard interface;

FIG. 35 is a view for explaining a process of converting an HDR into apseudo HDR;

FIG. 36A is a view illustrating an example of an EOTF (Electro-OpticalTransfer Function) which supports the HDR and the SDR, respectively;

FIG. 36B is a view illustrating an example of an inverse EOTF whichsupports the HDR and the SDR, respectively;

FIG. 37 is a block diagram illustrating a configuration of a convertingdevice and the display device according to an exemplary embodiment;

FIG. 38 is a flowchart illustrating a converting method and a displaymethod performed by the converting device and the display deviceaccording to the exemplary embodiment;

FIG. 39A is a view for explaining first luminance conversion;

FIG. 39B is a view for explaining another example of the first luminanceconversion;

FIG. 40 is a view for explaining second luminance conversion;

FIG. 41 is a view for explaining third luminance conversion; and

FIG. 42 is a flowchart illustrating a detailed process of displaysettings.

DETAILED DESCRIPTION

A transmitting method according to one aspect of the present disclosureis a method used by a playback device, and includes: when a version of atransmission protocol is a first version, transmitting first meta datato a display device without transmitting second meta data to the displaydevice, the transmission protocol being used to transmit a signalbetween the playback device and the display device, the first meta dataincluding information that is commonly used for a plurality of imagesincluded in a continuous playback unit of a first video signal andrelates to a luminance range of the first video signal, the second metadata including information that is commonly used for a unit subdividedcompared to the continuous playback unit of the first video signal andrelates to the luminance range of the first video signal; and when theversion of the transmission protocol is a second version, transmittingthe first meta data and the second meta data to the display device.

Consequently, according to this transmitting method, it is possible totransmit appropriate meta data of the first meta data and the secondmeta data, to the display device according to the version of thetransmission protocol.

For example, when the version of the transmission protocol is the firstversion, a conversion process of converting the luminance range of thefirst video signal may be performed by using the second meta data toobtain a second video signal, and the second video signal may betransmitted to the display device.

Consequently, when the second meta data cannot be transmitted to thedisplay device and the display device cannot perform a conversionprocess, the playback device can perform the conversion process.

For example, when the version of the transmission protocol is the secondversion and the display device does not include a function of theconversion process of converting the luminance range of the first videosignal by using the second meta data, the conversion processing may beperformed to obtain a second video signal, and the second video signalmay be transmitted to the display device, and when the version of thetransmission protocol is the second version and the display deviceincludes the function of the conversion process, the first video signalmay be transmitted to the display device without performing theconversion process.

Consequently, appropriate one of the playback device and the displaydevice can execute a conversion process.

For example, when the playback device does not include a function of theconversion process of converting the luminance range of the video signalby using the second meta data, the conversion processing may not beperformed, and the second meta data may not be transmitted to thedisplay device.

For example, a luminance value of the first video signal may be encodedas a code value, and the first meta data may be the information forspecifying an EOTF (Electro-Optical Transfer Function) of associating aplurality of luminance values and a plurality of code values.

For example, the second meta data may indicate mastering characteristicsof the first video signal.

Further, a playback method according to one aspect of the presentdisclosure is a playback method for playing back a video signal, aluminance of the video signal being a first luminance value in a firstluminance range whose maximum luminance value is defined as a firstmaximum luminance value exceeding 100 nit, the playback methodincluding: determining whether or not an inter-screen change amount of aluminance value of the video signal exceeds a predetermined firstthreshold; and adjusting the luminance value of the video signal when itis determined that the change amount exceeds the first threshold.

Consequently, according to the playback method, when a luminance valueof a video signal exceeds display capability of the display device, itis possible to generate a video signal which the display device canappropriately display by lowering the luminance value of the videosignal. Further, according to the playback method, when a large changeamount of a luminance value of a video signal is likely to negativelyinfluence viewers, it is possible to reduce the negative influence bylowering the luminance value of the video signal.

For example, the adjustment may include adjusting, for a pixel whosechange amount exceeds the first threshold, a luminance value of thepixel such that the change amount of the pixel is the first threshold orless.

For example, the determination may include determining whether or not adifference exceeds the first threshold, the difference being adifference between a peak luminance of a first image included in thevideo signal, and each of luminance values of a plurality of pixelsincluded in the video signal and included in a second image subsequentto the first image, and the adjustment may include adjusting, for apixel whose difference exceeds the first threshold, a luminance value ofthe pixel such that the difference of the pixel is the first thresholdor less.

For example, the determination may include determining whether or notthe change amount of the luminance value at a reference time intervalexceeds the first threshold, the reference time interval being aninteger multiple of a reciprocal of a frame rate of the video signal.

For example, the determination may include determining whether or not arate of pixels whose change amounts exceed the first threshold withrespect to a plurality of pixels exceeds a second threshold, theplurality of pixels being included in an image included in the videosignal, and the adjustment may include adjusting, when the rate exceedsthe second threshold, the luminance values of a plurality of pixels suchthat the rate is the second threshold or less.

For example, the determination may include determining, for each of aplurality of areas obtained by dividing a screen, whether or not theinter-screen change amount of the luminance value of each of a pluralityof areas exceeds the first threshold, and the adjustment may includeperforming adjustment process of lowering a luminance value of an areafor which it is determined that the change amount exceeds the firstthreshold.

Further, a playback method according to one aspect of the presentdisclosure is a playback method for playing back a video signal, aluminance of the video signal being a first luminance value in a firstluminance range whose maximum luminance value is defined as a firstmaximum luminance value exceeding 100 nit, the playback methodincluding: determining whether or not a luminance value of an image ofthe video signal exceeds a predetermined first threshold; and adjustingthe luminance value of the image when determining that the luminancevalue exceeds the first threshold.

Consequently, according to the playback method, when a luminance valueof a video signal exceeds display capability of the display device, itis possible to generate a video signal which the display device canappropriately display by lowering the luminance value of the videosignal. Further, according to the playback method, when a high luminancevalue of a video signal is likely to negatively influence viewers, it ispossible to reduce the negative influence by lowering the luminancevalue of the video signal.

For example, the determination may include determining, whether or not anumber of pixels whose luminance values exceed the first threshold withrespect to a plurality of pixels included in the image exceeds the firstthreshold, and the adjustment may include lowering, when the number ofpixels exceeds a third thresholds, the luminance value of the image suchthat the number of pixels is the third threshold or less.

For example, the determination may include determining, a rate of pixelswhose luminance values exceed the first threshold with respect to aplurality of pixels included in the image, and the adjustment mayinclude lowering, when the rate exceeds a third threshold, the luminancevalue of the image such that the rate is the third threshold or less.

For example, the first threshold may be a value calculated based on anupper limit value of a voltage which is simultaneously applicable to aplurality of pixels in a display device that displays the video signal.

Further, a playback device according to one aspect of the presentdisclosure is a playback device that transmits a video signal to adisplay device, and includes one or more memories and circuitry which,in operation: transmits, when a version of a transmission protocol is afirst version, first meta data to the display device withouttransmitting second meta data to the display device, the transmissionprotocol being used to transmit a signal between the playback device andthe display device, the first meta data including information that iscommonly used for a plurality of images included in a continuousplayback unit of a first video signal and relates to a luminance rangeof the first video signal, the second meta data including informationthat is commonly used for a unit subdivided compared to the continuousplayback unit of the first video signal and relates to the luminancerange of the first video signal; and transmits, when the version of thetransmission protocol is a second version, the first meta data and thesecond meta data to the display device.

Consequently, the playback device can transmit appropriate meta data ofthe first meta data and the second meta data, to the display deviceaccording to the version of the transmission protocol.

Furthermore, a playback device according to one aspect of the presentdisclosure is a playback device that plays back a video signal, aluminance of the video signal being a first luminance value in a firstluminance range whose maximum luminance value is defined as a firstmaximum luminance value exceeding 100 nit, the playback device includingone or more memories and circuitry which, in operation: determineswhether or not an inter-screen change amount of a luminance value of thevideo signal exceeds a predetermined first threshold; and adjusts theluminance value of the video signal when it is determined that thechange amount exceeds the first threshold.

Consequently, when a luminance value of a video signal exceeds displaycapability of the display device, the playback device can generate avideo signal which the display device can appropriately display bylowering the luminance value of the video signal. Further, when a largechange amount of a luminance value of a video signal is likely tonegatively influence viewers, the playback device can reduce thenegative influence by lowering the luminance value of the video signal.

Furthermore, a playback device according to one aspect of the presentdisclosure is a playback device that plays back a video signal, aluminance of the video signal being a first luminance value in a firstluminance range whose maximum luminance value is defined as a firstmaximum luminance value exceeding 100 nit, the playback device includingone or more memories and circuitry which, in operation: determineswhether or not a luminance value of an image included in the videosignal exceeds a predetermined first threshold; and adjusts theluminance value of the image when it is determined that the luminancevalue exceeds the first threshold.

Consequently, when a luminance value of a video signal exceeds displaycapability of the display device, the playback device can generate avideo signal which the display device can appropriately display bylowering the luminance value of the video signal. Further, when a highluminance value of a video signal is likely to negatively influenceviewers, the playback device can reduce the negative influence bylowering the luminance value of the video signal.

In addition, these comprehensive or specific aspects may be realized bya system, a method, an integrated circuit, a computer program or acomputer-readable recording medium such as a CD-ROM, and may be realizedby an arbitrary combination of the system, the method, the integratedcircuit, the computer program and the recording medium.

Further, the above features will be mainly described in [27. HDR MetaData Transmitting Method] to [28. Adjustment of Luminance Value].

In addition, the exemplary embodiment described below is a comprehensiveor specific example. Numerical values, shapes, materials, components,placement positions and connection modes of the components, steps and astep order described in the following exemplary embodiment areexemplary, and by no means limit the present disclosure. Further,components which are not recited in the independent claims representingthe uppermost generic concepts among components in the followingexemplary embodiment will be described as arbitrary components.

Exemplary Embodiment 1. Background

First, a transition of a video technology will be described withreference to FIG. 1. FIG. 1 is a view for explaining development of thevideo technology.

Expanding a number of display pixels has been mainly focused to providehigh-quality video images so far. So-called 2K video images of videoimages of 720×480 pixels of Standard Definition (SD) to 1920×1080 pixelsof High Definition (HD) are spreading.

In recent years, introduction of so-called 4K video images of 3840×1920pixels of Ultra High Definition (UHD) or 4096×1920 pixels of 4K has beenstarted to provide much higher quality of video images.

Further, providing higher resolutions of video images by introducing 4K,and providing higher quality video images by extending a dynamic rangeand expanding a color gamut or by adding and improving a frame rate havebeen studied.

Above all, as a dynamic range, an HDR (High Dynamic Range) is a methodfor supporting a luminance range whose maximum luminance value isexpanded to express, with a brightness close to an actual brightness,bright light such as specular reflection light which cannot be expressedby existing TV signals while maintaining a dark part gradation inconventional video images, and is gaining attention. More specifically,a method for a luminance range supported by conventional TV signals iscalled an SDR (Standard Dynamic Range) and has 100 nit of a maximumluminance value. Meanwhile, the HDR is assumed to expand the maximumluminance value to 1000 nit or more. The HDR is being standardized bySMPTE (Society of Motion Picture & Television Engineers) and ITU-R(International Telecommunications Union Radiocommunications Sector).

Similar to HD and UHD, specific HDR application targets includebroadcasts, package media (Blu-ray (registered trademark which applieslikewise below) Discs), and Internet distribution.

In addition, a luminance of a video image which supports the HDR takes aluminance value of an HDR luminance range, and a luminance signalobtained by quantizing the luminance value of the video image will bereferred to as an HDR signal. A luminance of a video image whichsupports the SDR takes a luminance value of an SDR luminance range, anda luminance signal obtained by quantizing the luminance value of thevideo image will be referred to as an SDR signal.

2. Object and Task

An HDR (High Dynamic Range) signal which is an image signal of a higherluminance range than that of conventional image signals is distributedvia a package medium such as a Blu-ray disc in which HDR signals arestored, broadcasting or a distribution medium such as a OTT (Over TheTop). In this regard, the OTT means Web sites provided on the Internet,content and services such as moving images and audios or providers whichprovide the content and services. Distributed HDR signals are decoded bya Blu-ray device or the like. Further, decoded HDR signals are sent toan HDR supporting display device (TVs, projectors, tablets orsmartphones), and the HDR supporting display device plays back HDR videoimages.

The HDR technique is only at an early stage, and it is assumed that,after an HDR technique which is introduced first is adopted, a new HDRmethod is developed. In this case, it is possible to adopt a new HDRmethod by storing an HDR signal (and meta data) of a newly created HDRmethod, in an HDR distribution medium. In this case, what is importantis “Forward Compatibility” which means that an original device (e.g.Blu-ray device) which does not support a new function can play back anHDR distribution medium in which signals of a new HDR method are stored.The present disclosure realizes a method and a device which maintain,for a distribution medium in which a new HDR signal format (meta data)is stored, compatibility by guaranteeing HDR playback of an originaltechnique without changing a decoding device (e.g. Blu-ray device)designed for an original distribution medium, and enable an HDR decodingdevice (e.g. Blu-ray device) which supports a new method to support aprocess of a new HDR method.

Further, when a method for adopting a new technique so randomly isadopted without selecting an extension method or appropriatelydetermining a registering method, a flood of multiple non-compatiblemethods is likely to cause confusion in the market. By contrast withthis, introduction of a very strict technique selection mechanism delaysdetermination of a new technique. Thus, the delay of the introduction oftechnical renovation is likely to make a distribution platform (e.g.Blu-ray) of the technique obsolete. Therefore, there is a risk that itis not possible to maintain competitiveness of this distributionplatform against other platforms (e.g. electronic distribution servicesuch as the OTT). Hence, an option introduction method which adoptsadvantages of both is necessary. In the present exemplary embodiment, ahybrid option introduction method which meets these needs is proposed.

FIG. 2 is a view illustrating an HDR position (expansion of aluminance). Further, FIG. 3 illustrates an image example indicating anHDR effect.

3. Relationship Between Masters, Distributing Methods and DisplayDevices During Introduction of HDR

FIG. 4 is a view illustrating a relationship between a flow of creatingSDR and HDR home entertainment masters, distribution media and displaydevices.

An HDR concept has been proposed, and effectiveness at a level of theHDR concept has been confirmed. Further, a first method for implementingan HDR has been proposed. In this regard, this does not mean that agreat number of items of HDR content has been created by using thismethod, and the first implementation method has not been substantiated.Hence, when creation of HDR content is earnestly advanced in future,meta data for an existing HDR creation method, an HDR-SDR convertingmethod or a tone mapping conversion method of a display device is likelyto change.

4. How to Use EOTF

FIG. 5 is an explanatory view of a method for determining a code valueof a luminance signal to be stored in content, and a process forrestoring a luminance value from a code value during playback.

A luminance signal indicating a luminance in the present exemplaryembodiment is an HDR signal which supports an HDR. A graded image isquantized by an HDR inverse EOTF, and a code value associated with aluminance value of the image is determined. The image is encoded basedon this code value, and a video stream is generated. During playback, astream decoding result is inversely quantized based on the HDR EOTF andis converted into a linear signal, and a luminance value of each pixelis restored. Quantization performed by using an HDR inverse EOTF will bereferred to as “HDR inverse EOTF conversion” below. Inverse quantizationperformed by using an HDR EOTF will be referred to as “HDR EOTFconversion” below. Similarly, quantization performed by using an SDRinverse EOTF will be referred to as “SDR inverse EOTF conversion” below.Inverse quantization performed by using an SDR EOTF will be referred toas “SDR EOTF conversion” below.

A video conversion processor performs conversion into a luminance valuewhich can be displayed by a video display, by using this luminance valueand meta data, and, consequently, the video display can display HDRvideo images. When, for example, a peak luminance of an original HDRvideo image is 2000 nit and a peak luminance of the video display is 800nit, it is possible to perform conversion and lower a luminance.

Thus, an HDR master method is realized by a combination of an EOTF, metadata and an HDR signal. Consequently, it is likely that a more efficientEOTF and meta data are developed, and a time to adopt an HDR methodusing such an EOTF and meta data comes.

In this regard, what new method will be like is not known at this pointof time, yet it is imaginable that it is likely that an EOTF is changedand meta data is added. In this case, HDR signals also change.

The present disclosure intends to make the HDR popular by reducing arisk that, even when an HDR transmission format is changed as describedabove, customers who have bought HDR supporting devices have to buy newdevices.

5. Meta Data

FIG. 6 is a view illustrating an example of HDR meta data. HDR meta dataincludes conversion auxiliary information used to change (DR conversion)a luminance range of a video signal, and HDR control information. Eachinformation is one of static HDR meta data provided in title units, forexample, and dynamic HDR meta data provided in frame units, for example.Further, static HDR meta data is classified into one of required metadata (basic data) and selected meta data (extension data), and dynamicHDR meta data is classified as selected meta data. In addition, eachinformation will be described in detail below.

Thus, the basic method can be implemented by using only static HDR metadata. Further, each extension method is designed so as not to influencea playback device (e.g. Blu-ray) of the basic method.

6. HDR Meta Data 1

Parameters of HDR content indicating characteristics during masteringinclude static HDR meta data which is fixed per title or per playlist,and dynamic HDR meta data which is variable per scene. In this regard, atitle and a playlist are information indicating video signals which arecontinuously played back. Hereinafter, video signals which arecontinuously played back will be referred to as continuous playbackunits.

For example, static HDR meta data includes at least one of a type of anEOTF function (curve), a 18% Gray value, a Diffuse White value, Kneepoint and Clip point. The EOTF is information obtained by associating aplurality of luminance values and a plurality of code values, and isinformation for changing a luminance range of a video signal. Otherpieces of information are attribute information related to a luminanceof a video signal. Therefore, it may be said that static HDR meta datais information related to a luminance range of a video signal and isinformation for specifying the luminance range of the video signal.

More specifically, the 18% Gray value and the Diffuse White valueindicate a luminance value (nit) of a video image whose brightness is apredetermined reference, in other words, indicate a reference brightnessof a video image. More specifically, the 18% Gray value indicates amastered luminance value (nit) obtained of an object whose brightness is18 nit before the mastering. The Diffuse White value indicates aluminance value (nit) corresponding to white.

Further, Knee point and Clip point are parameters of the EOTF function,and indicate points at which EOTF characteristics change. Morespecifically, Knee point indicates a change point at which an increaseof a luminance value (output luminance) mapped as a luminance of a videosignal to the EOTF with respect to an increase of an original luminancevalue (input luminance) during shooting is a value different from 1:1.For example, Knee point is information for specifying a point which isoff from a linear change in FIG. 39A described below. Further, Clippoint indicates a point at which clipping starts in the EOTF function.In this regard, clipping refers to converting an input luminance valueof a given value or more into an identical output luminance value. Forexample, Clip point indicates a point at which an output luminance valuestops changing in FIG. 39B described below.

Further, types of the EOTF function (curve) include an HDR EOTF and anSDR EOTF illustrated in FIG. 36A, for example.

Thus, a content data generating method according to the presentexemplary embodiment is a content data generating method for generatingcontent data, and includes: a first generating step of generating videosignals, and static HDR meta data (first meta data) includinginformation which is commonly used for a plurality of images (videosignals configuring continuous playback units) included in thecontinuous playback units of the video signals, and which relates to aluminance range of the video signals; and a second generating step ofgenerating content data by associating the continuous playback units andthe static HDR meta data. For example, the information which relates tothe luminance range of the video signals is information for convertingthe luminance range of the video signals.

Further, the static HDR meta data includes information for specifying anEOTF of associating a plurality of luminance values and a plurality ofcode values. Furthermore, a luminance value of the video signal isencoded as a code value.

Still further, the static HDR meta data further includes informationindicating a luminance value of a video signal whose brightness is apredetermined reference or information indicating a point at which EOTFcharacteristics change. For example, the static HDR meta data includesinformation (Diffuse White value) indicating a luminance valuecorresponding to white of a video signal.

Further, in the first generating step, dynamic HDR meta data (secondmeta data) which is information commonly used for units subdividedcompared to the continuous playback units and which is informationrelated to the luminance range of the video signals is furthergenerated. For example, the information related to the luminance rangeof the video signals is information for converting the luminance rangeof the video signals.

The dynamic HDR meta data is a parameter indicating masteringcharacteristics which are different per scene. The masteringcharacteristics described herein indicate a relationship between anoriginal (pre-mastering) luminance and a mastered luminance. Forexample, the parameter indicating the mastering characteristics is sameinformation as the above static HDR meta data, in other words, at leastone of pieces of information included in the static HDR meta data.

FIG. 7 is a view illustrating a storage example of static HDR meta data.This example is an example where static HDR meta data is stored in aplaylist in a package medium such as a Blu-ray disc.

The static HDR meta data is stored as one of items of meta data of eachstream to which a reference is made from a playlist. In this case, thestatic HDR meta data is fixed in playlist units. That is, the static HDRmeta data is associated with each playlist and stored.

Further, according to the OTT, static HDR meta data may be stored in amanifest file to which a reference is made before a stream is obtained.That is, according to the content data generating method according tothe present exemplary embodiment, a video signal may be generated as avideo stream, and static HDR meta data may be stored in a manifest fileto which a reference is made before the video stream is obtained.

Further, in case of broadcasting, static HDR meta data may be stored ina descriptor indicating a stream attribute. That is, according to thecontent data generating method according to the present exemplaryembodiment, content data may be generated as a video stream, and staticHDR meta data may be stored as an identifier indicating a video streamattribute independently from the video stream. For example, the staticHDR meta data can be stored as a descriptor according to MPEG2-TS(Moving Picture Experts Group 2-Transport Stream).

Further, when static HDR meta data is fixed per title, static HDR metadata may be stored as management information indicating a titleattribute.

Furthermore, in this example, static HDR meta data for an HDR is storedby using a mechanism which stores various items of meta data in aplaylist in a Blu-ray disc. Hence, a presence of static HDR meta dataneeds to be defined in a playlist from a viewpoint of applicationstandards or a device such of Blu-ray or the like. Hence, it isnecessary to revise Blu-ray standards to newly provide new HDR staticmeta data. Further, a capacity is defined, and therefore it is difficultto limitlessly store items of static HDR meta data for an HDR optiontechnique.

7. HDR Meta Data 2

FIG. 8 is a view illustrating an example where dynamic HDR meta data isstored in a video stream. According to MPEG-4 AVC (Advanced VideoCoding) or HEVC (High Efficiency Video Coding), information related tostream playback control is stored by using a data structure called SEI(Supplemental Enhancement Information). Hence, for example, dynamic HDRmeta data is stored in SEI.

The dynamic HDR meta data is assumed to be updated per scene. A scenehead is a head access unit (AU) in random access units such as GOP(Group Of Pictures). Hence, dynamic HDR meta data may be stored in ahead access unit in a decoding order in the random access units. Thehead access unit in the random access units is an IDR (InstantaneousDecoder Refresh) picture or a non-IDR I picture to which a SPS (SequenceParameter Set) is added. Hence, a receiving-side device can obtaindynamic HDR meta data by detecting a NAL (Network Abstraction Layer)unit configuring a head access unit in the random access units.Alternatively, a unique type may be allocated to SEI in which dynamicHDR meta data is stored.

In addition, a type of the EOTF function may be stored as streamattribute information of a SPS. That is, according to the content datagenerating method according to the present exemplary embodiment, contentdata may be generated as a video stream encoded according to HEVC, andinformation for specifying the EOTF may be stored in a SPS included in avideo stream.

Further, in this example, a mechanism which stores option data accordingto MPEG is used, and dynamic HDR meta data is stored in a videoelementary stream. Hence, a presence of dynamic HDR meta data is notknown from a viewpoint of application standards or a device of Blu-rayor the like. Hence, it is possible to record dynamic HDR meta data byusing only the mechanism which stores option data according to MPEGwithout revising the Blu-ray standards. Further, an area to be used is aSEI area, so that it is also possible to store a plurality of items ofoption dynamic HDR meta data.

8. Method for Storing Dynamic HDR Meta Data

FIG. 9 is a view illustrating an example where dynamic HDR meta data isstored in a TS stream format different from that of a main video image.

Blu-ray has a function of synchronizing and playing back two TS streams.This two TS stream synchronizing/playback function includes a 2TSplayback function of synchronizing and playing back two individuallymanaged TS streams in a disk, and a 1TS playback function ofinterleaving two streams to use as one TS stream.

By using this two TS stream synchronizing/playback function and storingdynamic HDR meta data in a TS stream format, the playback device can usedynamic HDR meta data in synchronization with main HDR video images.Consequently, a normal HDR player can play back only main HDR videoimages, and obtain video images of standard HDR quality. Further, anoption supporting HDR player can play back high gradation HDR qualityvideo images by using dynamic HDR meta data stored in a TS.

In this example, dynamic HDR meta data is stored in an auxiliary TSstream by using a mechanism which stores two TS streams of Blu-ray.Hence, a presence of dynamic HDR meta data is recognized as a TS streamfrom a viewpoint of application standards or a device of Blu-ray or thelike. Hence, it is necessary to revise the Blu-ray standards. Further,it is possible to simultaneously store TS streams of two types ofoptions.

9. Method for Transmitting Static HDR Meta Data

FIG. 10 is a view illustrating a method for transmitting static HDR metadata. FIG. 10 illustrates a flowchart illustrating an example of anoperation of transmitting an HDR signal to a display device from aplayback device such as a BD player (Blu-ray device) or a recorderaccording to a transmission protocol such as HDMI.

That static HDR meta data is fixed in title units or playlist units hasbeen described above. Hence, when it is necessary to set static HDR metadata (Yes in S401), the playback device obtains the static HDR meta datafrom content management information during a start of playback of atitle or a playlist, and stores and transmits the obtained static HDRmeta data as HDMI control information. That is, prior to a start oftransmission of a video signal configuring a title or a playlist, theplayback device obtains static HDR meta data corresponding to the titleor the playlist, and transmits the obtained static HDR meta data as HDMIcontrol information (S402). More generally, the playback device maytransmit static HDR meta data as initialization information when a HDMIinitialization process between the playback device and the displaydevice is performed.

Subsequently, the playback device transmits a video stream correspondingto the static HDR meta data (S403). In addition, transmitted static HDRmeta data is effective for this video stream.

Thus, a video stream transmitting method according to the presentexemplary embodiment is a video stream transmitting method fortransmitting a video stream (video stream), and includes: an obtainingstep of obtaining content data including video signals, and static HDRmeta data (first meta data) which is information which is commonly usedfor a plurality of images included in the continuous playback units, andwhich relates to a luminance range of the video signals; and atransmitting step of transmitting a video stream corresponding to thevideo signals, and static HDR meta data.

For example, in the transmitting step, the video stream and the staticHDR meta data are transmitted according to a HDMI communicationprotocol.

Further, the dynamic HDR meta data is transmitted as part of a videostream (SEI).

In addition, the playback device may transmit dynamic HDR meta data as aHDMI control signal at a timing at which the dynamic HDR meta databecomes effective. In this case, the playback device providesidentifiers for the static HDR meta data and the dynamic HDR meta datato be identified from each other, and transmit the static HDR meta dataand the dynamic HDR meta data.

Further, only a data structure of a container for storing dynamic HDRmeta data may be defined in a control signal, and a copy of contents ofSEI may be enabled as payload data of the container. Consequently, it ispossible to support even an update of a syntax of dynamic HDR meta dataincluded in SEI without changing the mounted playback device such as aBD player.

Similarly, by enabling copy and transmission of static HDR meta data incontent management information, it is possible to support a change of asyntax of the static HDR meta data without changing the mounted playbackdevice. That is, a data structure of a container for storing static HDRmeta data is defined, so that, in the transmitting step, the static HDRmeta data included in content data may be copied to a payload of thecontainer to transmit the container.

Further, dynamic HDR meta data stored in a TS stream is synthesized witha main HDR video signal by some method, and is transmitted as a newvideo signal (high gradation HDR video images in an example in FIG. 9)according to HDMI.

10. Method for Processing HDR Meta Data

FIG. 11 is a flowchart illustrating an example of a method forprocessing HDR meta data in case where the display device displays anHDR signal. First, the display device obtains static HDR meta data fromHDMI control information (S411), and determines a method for displayingan HDR signal based on the obtained static HDR meta data (S412).

In addition, when the control information does not include the staticHDR meta data, the display device determines a method for displaying anHDR signal based on a predetermined value of application standards ordefault settings of the display device. That is, according to the videodisplay method according to the present exemplary embodiment, whenstatic HDR meta data cannot be obtained, a video display method matchinga video signal is determined based on the predetermined value or thesettings.

Further, when detecting dynamic HDR meta data in SEI in a video stream(Yes in S413), the display device updates a method for displaying an HDRsignal based on the dynamic HDR meta data (S414). That is, according tothe video display method according to the present exemplary embodiment,when static HDR meta data is obtained, a display method is determinedbased on the obtained static HDR meta data to display video images.Further, when dynamic HDR meta data is obtained, the display methoddetermined based on the static HDR meta data is updated to the displaymethod determined based on dynamic HDR meta data to display videoimages. Alternatively, a display method may be determined based on bothof static HDR meta data and dynamic HDR meta data.

In addition, when the display device does not support obtaining dynamicHDR meta data, the display device may operate based only on static HDRmeta data. Further, even when the display device supports obtainingdynamic HDR meta data, the display device cannot update a method fordisplaying an HDR signal in synchronization with a presentation timestamp (PTS) of an access unit in which meta data is stored in somecases. In this case, after obtaining meta data, the display device mayupdate a display method from an access unit displayed subsequent to theearliest time at which the display method can be updated.

In addition, it is possible to update and add parameters by allocatingversion information to HDR meta data. Consequently, the display devicecan determine whether or not it is possible to interpret HDR meta databased on version information of the HDR meta data. Alternatively, HDRmeta data may be configured by a basic portion and an extension portion,and a parameter may be updated or added by changing the extensionportion without updating the basic portion. That is, each of static HDRmeta data and dynamic HDR meta data may include a plurality of versions,and may include a basic portion which is commonly used between aplurality of versions, and an extension portion which differs perversion. By so doing, it is possible to secure backward compatibility ofthe display device based on HDR meta data of the basic portion.

Thus, the video display method according to the present exemplaryembodiment is a video display method for displaying video images basedon video streams, and includes: an obtaining step of obtaining a videostream corresponding to the video signals, and static HDR meta data(first meta data); and a display step of determining a display methodfor displaying the video images corresponding to the video signals basedon the static HDR meta data and displaying the video image.

Further, a luminance value of the video signal is encoded as a codevalue. Static HDR meta data includes information for specifying an EOTFof associating a plurality of luminance values and a plurality of codevalues. In the display step, video images are generated by using theEOTF specified by the static HDR meta data and converting the code valueindicated by the video signal into a luminance value

11. Data Output Device

FIG. 12 is a block diagram illustrating a configuration of data outputdevice 400 such as a BD layer which outputs HDR signals. HDR meta datainput to data output device 400 includes characteristics data indicatingmastering characteristics of an HDR signal, and conversion auxiliarydata indicating a tone mapping method for converting an HDR signal intoan SDR signal or for converting a dynamic range of the HDR signal. Thesetwo types of items of meta data are stored as static HDR meta data ordynamic HDR meta data as described with reference to FIGS. 7 and 8.Further, the static HDR meta data is stored in at least one of contentmanagement information and a video stream.

Data output device 400 includes video decoder 401, external metaobtaining unit 402, HDR meta interpreter 403, HDR control informationgenerator 404, DR converter 405 and HDMI output unit 406.

Video decoder 401 generates a video signal (first video signal) bydecoding a video stream which is a video encoded stream, and outputs theresulting video signal to DR converter 405. Further, video decoder 401obtains HDR meta data (second meta data) (static HDR meta data ordynamic HDR meta data) in the video stream. More specifically, videodecoder 401 outputs to HDR meta interpreter 403 HDR meta data stored ina SEI message or the like according to MPEG-4 AVC or HEVC.

External meta obtaining unit 402 obtains static HDR meta data (firstmeta data) stored in the content management information such as aplaylist, and outputs the obtained static HDR meta data to HDR metainterpreter 403. In this regard, in the content management information,dynamic HDR meta data which can be changed in predetermined units, suchas a playitem, which enable a random access may be stored. In this case,external meta obtaining unit 402 obtains dynamic HDR meta data from thecontent management information, and outputs the obtained dynamic HDRmeta data to HDR meta interpreter 403.

HDR meta interpreter 403 determines a type of HDR meta data output fromvideo decoder 401 or external meta obtaining unit 402, outputscharacteristics data to HDR control information generator 404 andoutputs conversion auxiliary data to DR converter 405.

In addition, when both of video decoder 401 and external meta obtainingunit 402 obtain static HDR meta data, only the static HDR meta dataoutput from external meta obtaining unit 402 may be used as effectivemeta data. That is, there is a case where the first meta data obtainedby external meta obtaining unit 402 and the second meta data obtained byvideo decoder 401 are static HDR meta data which is commonly used for aplurality of images included in continuous playback units of the firstvideo signal. In this case, when both of the first meta data and thesecond meta data are obtained, HDR meta interpreter 403 obtainscharacteristics data and conversion auxiliary data by analyzing thefirst meta data.

Alternatively, HDR meta interpreter 403 may use static HDR meta data aseffective meta data when external meta obtaining unit 402 obtains thestatic HDR meta data, and may overwrite static HDR meta data over theeffective meta data when video decoder 401 obtains the static HDR metadata. That is, there is a case where the first meta data obtained byexternal meta obtaining unit 402 and the second meta data obtained byvideo decoder 401 are static HDR meta data which is commonly used for aplurality of images included in continuous playback units of the firstvideo signal. In this case, when only the first meta data of the firstmeta data and the second meta data is obtained, HDR meta interpreter 403obtains characteristics data and conversion auxiliary data by analyzingthe first meta data. When the second meta data is obtained, HDR metainterpreter 403 switches meta data to use from the first meta data tothe second meta data.

HDR control information generator 404 generates HDR control informationaccording to HDMI based on the characteristics data, and outputs thegenerated HDR control information to HDMI output unit 406. In thisregard, as for dynamic HDR meta data, an output timing of HDR controlinformation in HDMI output unit 406 is determined such that it ispossible to output HDR control information in synchronization with avideo signal whose meta data is effective. That is, HDMI output unit 406outputs HDR control information in synchronization with a video signal(video signal) whose meta data is effective.

DR converter 405 converts a decoded video signal into an SDR signal andconverts a dynamic range based on conversion auxiliary data. In thisregard, when the display device connected with data output device 400supports an input of HDR signals, DR converter 405 does not need toperform conversion. Hence, by checking whether or not the connectiondestination display device supports an input of HDR signals by aninitialization process according to HDMI, data output device 400 maydetermine whether or not conversion process is necessary. When it isdetermined that the conversion process is unnecessary, a first videosignal obtained by video decoder 401 is input to HDMI output unit 406without DR converter 405.

That is, HDMI output unit 406 outputs the first video signal and the HDRcontrol information to the display device when the display deviceconnected to data output device 400 supports a video output of aluminance range of the HDR signal (first video signal). Further, HDMIoutput unit 406 outputs a second video signal obtained by converting anHDR into an SDR, and the HDR control information to the display devicewhen the display device connected to data output device 400 does notsupport a video output of a luminance range of the HDR signal (firstvideo signal). Furthermore, HDMI output unit 406 determines whether ornot the display device supports a video output of a luminance range ofan HDR signal (first video signal) by a transmission protocol (e.g.HDMI) initialization process.

HDMI output unit 406 outputs the video signal output from DR converter405 or video decoder 401 and the HDR control information according to aHDMI protocol.

In addition, data output device 400 can use the same configuration evenwhen receiving and outputting broadcast or OTT content. Further, whendata output device 400 and the display device are included in a singledevice, HDMI output unit 406 is not necessary.

Furthermore, as described above, data output device 400 includesexternal meta obtaining unit 402 which obtains meta data from controlinformation or the like, and video decoder 401 includes a function ofobtaining meta data from a video stream. However, data output device 400may include one of external meta obtaining unit 402 and the function.

Further, an example where data output device 400 outputs data (the videosignal and the HDR control information) according to HDMI has beendescribed above.

However, data output device 400 may output data according to anarbitrary transmission protocol.

Thus, data output device 400 includes: a decoder (video decoder 401)which generates a first video signal of a first luminance range (HDR) bydecoding a video stream; an obtaining unit (at least one of videodecoder 401 and external meta obtaining unit 402) which obtains firstmeta data related to a luminance range of the first video signal; aninterpreter (HDR meta interpreter 403) which obtains characteristicsdata indicating the luminance range of the first video signal byinterpreting the first meta data; a control information generator (HDRcontrol information generator 404) which converts the characteristicsdata into HDR control information according to a predeterminedtransmission protocol (e.g. HMDI); and an output unit (HDMI output unit406) which outputs the HDR control information according to thepredetermined transmission protocol.

Consequently, data output device 400 can generate the controlinformation based on the characteristics data included in the meta data.

Further, the interpreter (HDR meta interpreter 403) further obtainsconversion auxiliary data for converting a luminance range of a firstvideo signal, by interpreting the first meta data. Data output device400 further includes a converter (DR converter 405) which generates asecond video signal of a luminance range narrower than the luminancerange of the first video signal by converting the luminance range of thefirst video signal based on the conversion auxiliary data. The outputunit (HDMI output unit 406) further outputs at least one of the firstvideo signal and the second video signal according to the predeterminedtransmission protocol.

Consequently, data output device 400 can change the luminance range ofthe first video signal by using the conversion auxiliary data includedin the meta data.

Further, the decoder (video decoder 401) obtains the second meta data(HDR meta data) related to the luminance range of the first video signalfrom the video stream. The interpreter (HDR meta interpreter 403)obtains characteristics data and the conversion auxiliary data byanalyzing at least one of the first meta data and the second meta data.

Further, as illustrated in FIG. 6, static HDR meta data includesrequired meta data and selected meta data, and dynamic HDR meta dataincludes only selected meta data. That is, static HDR meta data is usedat all times, and dynamic HDR meta data is selectively used. Thus, thefirst meta data obtained by external meta obtaining unit 402 or thesecond meta data obtained by video decoder 401 includes static HDR metadata (static meta data) which is commonly used for a plurality of imagesincluded in continuous playback units of a video signal and includescharacteristics data. HDR control information generator 404 converts thecharacteristics data included in the static HDR meta data into HDRcontrol information according to the predetermined transmissionprotocol. HDMI output unit 406 outputs the HDR control information basedon the static HDR meta data when outputting the first video signal (HDRsignal).

Further, the first meta data obtained by external meta obtaining unit402 or the second meta data obtained by video decoder 401 furtherincludes dynamic HDR meta data (dynamic meta data) which is commonlyused for units subdivided compared to the continuous playback units ofthe video signal and includes characteristics data. HDR controlinformation generator 404 converts the characteristics data included inthe static HDR meta data and the characteristics data included in thedynamic HDR meta data, into HDR control information according to thepredetermined transmission protocol. HDMI output unit 406 outputs theHDR control information based on the static HDR meta data and thedynamic HDR meta data when outputting the first video signal (HDRsignal).

Further, a data generating method according to the present disclosure isa data generating method performed by a data generating device, andincludes: a first generating step of generating meta data related to aluminance range of a video signal; and a second generating step ofgenerating a video stream including a video signal and meta data. Metadata includes characteristics data indicating the luminance range of thevideo signal, and conversion auxiliary data for converting the luminancerange of the video signal.

12. Storage Example 1 of HDR Meta Data

FIG. 13 is a view illustrating a data structure example of a SEI messagein which HDR meta data is stored. As illustrated in FIG. 13, an HDR metadata dedicated SEI message may be defined. That is, meta data may bestored in a meta data dedicated message.

Further, HDR meta data may be stored in a general-purpose user datastorage SEI message, and information (HDR extension identificationinformation described below) indicating that the HDR meta data is storedin a payload portion of the message may be provided.

HDR meta data includes static HDR meta data and dynamic HDR meta data.Further, flag information indicating whether or not static HDR meta datais stored, and flag information indicating whether or not dynamic HDRmeta data is stored may be provided. Thus, it is possible to use threetypes of storage methods including a method for storing only static HDRmeta data, a method for storing only dynamic HDR meta data and a methodfor storing both of the static HDR meta data and the dynamic HDR metadata.

Further, for each meta data, basic data (basic portion) which needs tobe interpreted, and extension data (extension portion) which isoptionally interpreted (whose interpretation is optional) may bedefined. For example, type information indicating a type of meta data(basic data or extension data), and a size are included in headerinformation, and a format of a container in which meta data is stored ina payload is defined. That is, meta data includes a payload, informationindicating whether payload data is basic data or extension data, andinformation indicating a payload data size. In other words, meta dataincludes type information indicating a type of meta data. For example,basic data is stored in a container whose type value is 0. Further, avalue equal to or more than 1 is allocated as a type value to theextension data, and this value indicates a type of the extension data.

The data output device and the display device refer to the type value,and obtain data of the container which the data output device and thedisplay device can interpret. That is, the data output device (or thedisplay device) determines whether or not the data output device (or thedisplay device) can interpret meta data, by using the type information,and obtains characteristics data and conversion auxiliary data byinterpreting the meta data when the data output device (or the displaydevice) can interpret the meta data.

Further, meta data may be generated such that a maximum size of HDR metadata is set in advance and a total sum of sizes of basic data andextension data is the maximum size or less. That is, a maximum value ofa data size of meta data is defined, and, according to the datagenerating method according to the present disclosure, the meta data isgenerated such that a total data size of the basic data and theextension data is the maximum value or less.

The data output device and the display device include memories whichsupport this maximum size and, consequently, can guarantee that all HDRmeta data can be stored in the memories. Alternatively, it is alsopossible to secure a data area corresponding to a fixed size of staticHDR meta data or dynamic HDR meta data, and to use an area other than anarea in which basic data is stored, for extension in future.

Such a data structure may be used to store HDR meta data in contentmanagement information.

By using a SEI area in this way, it is possible to relatively freelystore option information.

13. Storage Example 2 of HDR Meta Data

FIG. 14 is a view illustrating an example of a data structure in a casewhere HDR meta data is stored in a user data storage SEI message. Thedata structure is the same as the data structure in FIG. 14 except thata message includes HDR extension identification information and anextension type ID. The HDR extension identification informationindicates that the message includes HDR meta data. An extension type IDindicates an HDR meta data version or the like. That is, meta data isstored in a SEI message according to HEVC, and the SEI message includesHDR extension identification information indicating whether or not theSEI message includes meta data.

In this case, when the user data storage SEI message including the HDRextension identification information is received, and when the displaydevice connected to the data output device supports an input of an HDRsignal and HDR control information, the data output device copies andoutputs the received SEI message according to a protocol of an outputI/F such as HDMI for the display device. That is, when a SEI messageincluding HDR extension identification information indicating that metadata is included in the SEI message is obtained, and the data outputdestination display device supports an input of the HDR controlinformation, the data output device outputs the SEI message as isaccording to a predetermined transmission protocol (e.g. HDMI).

Consequently, irrespectively of meta data contents, the data outputdevice can output HDR meta data to the display device. According to thisconfiguration, even when a new DR conversion process is developed infuture to define new HDR meta data and a display device which supportsthis new HDR meta data is connected to a data output device which doesnot support new HDR meta data, it is possible to output new HDR metadata from the data output device to the display device. Further, thedisplay device can perform a DR conversion process matching new HDR metadata.

14. Storage Example of a Plurality of Items of HDR Meta Data

FIG. 15 is a view illustrating an example of a data structure in a casewhere a plurality of items of HDR meta data is stored in one user datastorage SEI message. In this SEI message, a plurality of items of HDRmeta data for a plurality of conversion modes (methods) related toconversion of a dynamic range (luminance range) is stored.

A field (a number of conversion modes) indicating the number ofconversion modes of providing HDR meta data is added to the datastructure illustrated in FIG. 15 compared to the data structureillustrated in FIG. 14. Further, a plurality of items of HDR meta datacorresponding to each conversion mode is stored in order subsequent tothe number of conversion modes.

That is, the data generating method according to the present exemplaryembodiment is a data generating method performed by the data generatingdevice, and includes: a first generating step of generating one or moreitems of meta data (HDR meta data) matching one or more conversion modesof converting a luminance range of a video signal; and a secondgenerating step of generating a video stream including a video signal,the one or more items of meta data, and the number of conversion modesindicating the number of one or more conversion modes.

15. Configuration of Data Output Device

FIG. 16 is a block diagram illustrating a configuration example of dataoutput device 500 according to the present exemplary embodiment. Thisdata output device 500 includes video decoder 501, external metaobtaining unit 502, HDR meta interpreter 503, HDR control informationgenerator 504, DR converter 505 and HDMI output unit 506. In addition,operations of HDR meta interpreter 503 and DR converter 505 aredifferent from those of data output device 400 illustrated in FIG. 12.That is, operations of video decoder 501, external meta obtaining unit502, HDR control information generator 504 and HDMI output unit 506 arethe same as operations of video decoder 401, external meta obtainingunit 402, HDR control information generator 404 and HDMI output unit406.

Further, data output device 500 is connected with display device 510(display), and outputs generated video signals and HDR controlinformation to display device 510 according to a predeterminedtransmission protocol such as HDMI.

DR converter 505 and display device 510 each support a plurality ofdynamic range conversion modes (converting methods). In this regard,“support” means having a function of performing a process of eachconversion mode. First, HDR meta interpreter 503 obtains static HDR metadata and dynamic HDR meta data from external meta obtaining unit 502 andvideo decoder 501. In content management information or encoded videostream, a plurality of items of HDR meta data for a plurality ofconversion modes is stored. HDR meta interpreter 503 determines aplurality of conversion modes matching a plurality of HDR meta data as aplurality of usable conversion modes.

Further, HDR meta interpreter 503 obtains information of a conversionmode of an HDR signal supported by display device 510 by communicatingwith display device 510 or via a network. Furthermore, HDR metainterpreter 503 determines (1) which one of data output device 500 anddisplay device 510 performs a dynamic range conversion process and (2) aconversion mode to use, based on (1) a conversion mode matching HDR metadata, (2) a conversion mode supported by DR converter 505 and (3) aconversion mode supported by display device 510.

When it is determined that data output device 500 performs theconversion process, DR converter 505 converts an HDR signal into an SDRsignal according to the conversion mode instructed by HDR metainterpreter 503. When it is determined that display device 510determines a conversion process, data output device 500 transmits avideo signal (HDR signal) to display device 510, and transmits HDR metadata which is necessary for conversion as a HDMI control signal (HDRcontrol information) to display device 510.

In addition, as described above, DR converter 505 supports a pluralityof conversion modes. However, DR converter 505 only needs to support oneor more conversion modes. In this case, data output device 500 onlyneeds to obtain one or more items of HDR meta data matching one or moreconversion modes.

Thus, data output device 500 includes: a decoder (video decoder 501)which generates a first video signal by decoding a video stream; anobtaining unit (at least one of video decoder 501 and external metaobtaining unit 502) which obtains one or more items of meta datamatching one or more first conversion modes of converting a luminancerange of the video signal; an interpreter (HDR meta interpreter 503)which obtains characteristics data indicating a luminance range of thefirst video signal and conversion auxiliary data for converting theluminance range of the first video signal, by interpreting one of one ormore items of first meta data; a control information generator (HDRcontrol information generator 504) which converts the characteristicsdata into HDR control information according to a predeterminedtransmission protocol (e.g. HMDI); a converter (DR converter 505) whichsupports one or more second conversion modes of converting a luminancerange of a video signal, and generates a second video signal of aluminance range narrower than the luminance range of the first videosignal by performing a process of converting the luminance range of thefirst video signal according to one of the one or more second conversionmodes based on the conversion auxiliary data; and an output unit (HDMIoutput unit 506) which outputs the second video signal and the HDRcontrol information to display device 510 according to the predeterminedtransmission protocol. The interpreter (HDR meta interpreter 503)further determines which one of data output device 500 and displaydevice 510 performs the above conversion process based on the one ormore first conversion modes, the one or more second conversion modes anda third conversion mode which is supported by display device 510 andconverts a luminance range of a video signal.

According to this, data output device 500 can determine which one ofdata output device 500 and display device 510 performs a conversionprocess based on the first conversion mode matching one or more items ofmeta data, the second conversion mode supported by data output device500 and the third conversion mode supported by display device 510.Consequently, data output device 500 can determine a device whichappropriately performs a conversion process.

In addition, the one or more second conversion modes supported by dataoutput device 500 may include at least part of a plurality of firstconversion modes matching the one or more items of meta data, or may notinclude any one of the one or more first conversion modes. Similarly,the third conversion mode supported by display device 510 may include atleast part of the one or more first conversion modes, or may not includeany one of the one or more first conversion modes. Further, the thirdconversion mode may include at least part of the one or more secondconversion modes, or may not include any one of the one or more secondconversion modes.

16. Configuration of DR Converter

A configuration example of DR converter 505 will be described below.FIG. 17 is a block diagram illustrating the configuration example of DRconverter 505. This DR converter 505 includes mode determining unit 511,N mode processors 512 and conversion result output unit 513. N modeprocessors 512 each support each of N conversion modes (processingmethods), and perform a process of a corresponding conversion mode. Modedetermining unit 511 obtains a conversion mode instructed by HDR metainterpreter 503, and determines mode processor 512 which performs aconversion process. That is, mode determining unit 511 selects modeprocessor 512 which supports the conversion mode instructed by HDR metainterpreter 503. Determined mode processor 512 generates an SDR signal(converted video signal) by performing a process of converting an HDRsignal (video signal). Conversion result output unit 513 outputs theconverted SDR signal.

FIG. 18 is a block diagram illustrating a configuration example of DRconverter 505A which is another example of DR converter 505. This DRconverter 505 includes mode determining unit 521, basic processor 522, Nextension mode processors 523 and conversion result output unit 524.

Basic processor 522 performs a default conversion process which is acommon process among N conversion modes. N extension mode processors 523perform a process performed by basic processor 522 and, in addition, anextension process of dynamically controlling parameters of a conversionprocess by using dynamic HDR meta data. Further, N extension modeprocessors 523 each support each of N conversion modes, and perform acorresponding conversion mode extension process. For example, basicprocessor 522 operates by using only static HDR meta data, and extensionmode processor 523 operates by using static HDR meta data and, inaddition, dynamic HDR meta data.

17. Operation Example of HDR Meta Interpreter

FIGS. 19 and 20 are views illustrating examples of instruction contentsof HDR meta interpreter 503 based on a conversion mode of providing HDRmeta data, whether or not data output device 500 supports each mode andwhether or not display device 510 supports each mode. HDR metainterpreter 503 basically selects an operation which maximizesreproducibility for a master image, from selectable combinations. Inthis regard, the master image refers to an image output without changinga luminance range.

For example, in an example illustrated in FIG. 19, data output device500 supports mode 1 and mode 2, and display device 510 does not supportany conversion mode. In addition, between mode 1 and mode 2, mode 2 hashigher reproducibility for the master image. Further, HDR metainterpreter 503 learns reproducibility of each mode for a master imagein advance. In this case, HDR meta interpreter 503 determines that dataoutput device 500 performs a conversion process, and selects mode 2 ofthe higher reproducibility between mode 1 and mode 2.

Further, in an example illustrated in FIG. 20, data output device 500supports mode 1, and display device 510 supports mode 1 and mode 2. Inthis case, HDR meta interpreter 503 determines that display device 510performs a conversion process, and selects mode 2 of the higherreproducibility between mode 1 and mode 2. Further, data output device500 outputs HDR meta data matching a conversion process of mode 2 asHDMI control information (HDR control information) to display device510. Display device 510 performs a conversion process of mode 2 by usingthe control information.

Thus, HDR meta interpreter 503 further determines as a conversion modeof a conversion process to be performed by data output device 500 aconversion mode which is included in the one or more first conversionmodes matching the one or more items of meta data and which is includedin the one or more second conversion modes supported by data outputdevice 500. More specifically, HDR meta interpreter 503 furtherdetermines as a conversion mode of a conversion process to be performedby data output device 500 or display device 510 a conversion mode whichis included in the one or more first conversion modes matching the oneor more items of meta data and which is included in at least one of theone or more second conversion modes supported by data output device 500and the third conversion mode supported by display device 510.

More specifically, HDR meta interpreter 503 determines as a conversionmode of a conversion process to be performed by data output device 500or display device 510 a conversion mode of the highest reproducibilityfor a master image among a plurality of conversion modes included in aplurality of first conversion modes and included in at least one of aplurality of second conversion modes and the third conversion mode.

In other words, data output device 500 selects a mode of the highestreproducibility among conversion modes supported by data output device500 and display device 510, and determines that one device of dataoutput device 500 and display device 510 supporting the selected modeperforms a conversion process.

More specifically, as illustrated in FIG. 19, HDR meta interpreter 503determines that data output device 500 performs a conversion processwhen the determined conversion mode of the conversion process isincluded in the second conversion modes and is not included in the thirdconversion mode. Further, as illustrated in FIG. 20, HDR metainterpreter 503 determines that display device 510 performs a conversionprocess when the determined conversion mode of the conversion process isincluded in the third conversion mode and is not included in the secondconversion modes.

According to this, data output device 500 can determine a conversionmode to use based on the first conversion modes matching one or moreitems of meta data, the second conversion modes supported by the dataoutput device and the third conversion mode supported by the displaydevice. Further, data output device 500 can select the conversion modeof the highest reproducibility for a master image and, consequently, canimprove quality of video images to be displayed.

FIG. 21 is a view illustrating an example where a conversion process isdetermined according to whether or not data output device 500 can obtainparameters of display device 510. A parameter of display device 510 is apeak luminance of display device 510 (a maximum value of a luminancerange which display device 510 can display) or a display mode whichdisplay device 510 can display. More specifically, this parameterindicates a currently viewing display mode as a display mode. Forexample, the display modes include a normal mode, a dynamic mode and acinema mode.

In an example illustrated in FIG. 21, data output device 500 supportsmode 1, mode 2 and mode 3, and display device 510 supports mode 1.Further, data output device 500 can obtain parameters of display device510 for mode 1 and mode 2, and cannot obtain a parameter of displaydevice 510 for mode 3. Furthermore, mode 2 has higher reproducibilitythan that of mode 1, and mode 3 has higher reproducibility than that ofmode 2.

In this case, a mode of the highest reproducibility among the modessupported by data output device 500 and display device 510 is mode 3.However, data output device 500 cannot obtain the parameter of displaydevice 510 for mode 3, and therefore mode 3 is excluded. Further, dataoutput device 500 selects mode 2 whose reproducibility is the secondhighest to that of mode 3 and whose parameter can be obtained, as aconversion mode to use. Furthermore, data output device 500 obtainsparameters which is necessary for mode 2, from display device 510, andperforms a conversion process of mode 2 by using the obtainedparameters.

Thus, HDR meta interpreter 503 further determines a conversion mode of aconversion process performed by data output device 500 or display device510 according to whether or not it is possible to obtain from displaydevice 510 parameters for each of a plurality of first conversion modesmatching a plurality of items of meta data. More specifically, HDR metainterpreter 503 determines as a conversion mode of a conversion processto be performed by data output device 500 or display device 510 aconversion mode which is included in a plurality of first conversionmodes and included in at least one of a plurality of second conversionmodes and the third conversion mode, and which makes it possible toobtain the parameters from display device 510.

That is, data output device 500 selects a mode of the highestreproducibility among the conversion modes supported by data outputdevice 500 and display device 510, and determines whether or not it ispossible to obtain a parameter of display device 510 for the selectedmode when only data output device 500 supports the selected mode. Whenthe parameter can be obtained, data output device 500 selects this mode.Meanwhile, when the parameter cannot be obtained, data output device 500selects another mode (a mode of the second highest reproducibility).

Thus, data output device 500 determines a conversion mode to useaccording to whether or not it is possible to obtain the parameter ofdisplay device 510 and, consequently, can select a more appropriateconversion mode.

18. Configuration Example 2 of Data Output Device

Another configuration example of the data output device will bedescribed below. FIG. 22 is a block diagram illustrating a configurationof data output device 500A. This data output device 500A furtherincludes DC 507 compared to data output device 500 illustrated in FIG.16. DC 507 down-converts a resolution of a video signal obtained byvideo decoder 501. For example, when a video signal is 4K, DC 507down-converts a 4K video signal into a 2K video signal.

According to this configuration, data output device 500A can selectivelyperform an operation of (1) converting a 4K HDR signal into a 2K HDRsignal to output, (2) converting the 4K HDR signal into the 2K HDRsignal, and then changing the dynamic range in DR converter 505 tooutput and (3) converting the 4K SDR signal into a 2K SDR signal tooutput, according to a resolution and a dynamic range supported bydisplay device 510. That is, data output device 500A can switch anoperation according to a resolution of display device 510 and whether ornot display device 510 supports an HDR signal.

FIG. 23 is a view illustrating an example of combinations ofcharacteristics of a video signal of content (a resolution and a dynamicrange (luminance range)), characteristics of display device 510 and anoutput signal of data output device 500A. Data output device 500Aselects a format of an output signal to match a resolution of displaydevice 510 and whether or not display device 510 supports an HDR signal,and controls DC 507 and DR converter 505 to generate an output signal ofthe selected format.

When, for example, a video signal of content is an HDR signal of a 4Kresolution, and display device 510 does not support displaying the HDRsignal of the 4K resolution and supports displaying an HDR signal of a2K resolution, data output device 500A converts the video signal of thecontent into an HDR signal of the 2K resolution to output (see thecombination example in the second row in FIG. 23). In this case, DC 507converts a resolution of a video signal.

Further, when a video signal of content is an HDR signal of a 4Kresolution, and display device 510 does not support displaying the HDRsignal of the 4K resolution and an HDR signal of a 2K resolution, andsupports displaying a 2K SDR signal, data output device 500A convertsthe video signal of the content into an SDR signal of the 2K resolutionto output (see the combination example in the third row in FIG. 23). Inthis case, DC 507 converts a resolution of a video signal, and DRconverter 505 converts a luminance range.

Consequently, display device 510 can more faithfully reproduce videosignals of content. In addition, data output device 500A may convert aresolution or display device 510 may operate to convert a dynamic rangeas described with reference to FIG. 16.

Thus, data output device 500A includes a down-converter (DC 507) whichgenerates a third video signal by lowering a resolution of the firstvideo signal obtained by video decoder 501. The converter (DR converter505) further generates a fourth video signal of a luminance rangenarrower than a luminance range of the third video signal by performinga process of converting the luminance range of the third video signalaccording to one of a plurality of second conversion modes based on theconversion auxiliary data. The output unit (HDMI output unit 506)further outputs the third video signal or the fourth video signal todisplay device 510.

Consequently, data output device 500A can change a resolution of a videosignal to, for example, a resolution suitable to display device 510 orthe like.

More specifically, when display device 510 does not support displaying avideo image of a resolution of the first video signal, (1) thedown-converter (DC 507) generates the third video signal and (2) theoutput unit (HDMI output unit 506) outputs the third video signal todisplay device 510. As illustrated in, for example, FIG. 23, when aresolution of a video signal is 4K and a resolution of display device510 is 2K, a 2K output signal is output.

Further, when display device 510 does not support displaying a videoimage of a luminance range (HDR) of the first video signal, (1) theconverter (DR converter 505) generates the second video signal of aluminance range (SDR) narrower than the luminance range (HDR) of thefirst video signal, and (2) the output unit (HDMI output unit 506)outputs the second video signal and HDR control information to displaydevice 510. When, for example, a dynamic range (luminance range) of avideo signal is an HDR and display device 510 does not support the HDR(in case of an SDR) as illustrated in FIG. 23, an HDR video signal isconverted into an SDR video signal and the SDR video signal (outputsignal) is output.

Further, when display device 510 does not support displaying a videoimage of the first video signal, and does not support displaying a videoimage of the luminance range (HDR) of the first video signal, (1) thedown-converter (DC 507) generates a third video signal, (2) theconverter (DR converter 505) generates the fourth video signal of aluminance range (SDR) narrower than the luminance range (HDR) of thethird video signal, and (3) the output unit (HDMI output unit 506)outputs the fourth video signal to display device 510. When, forexample, a resolution of a video signal is 4K, a dynamic range(luminance range) of the video signal is an HDR, the resolution ofdisplay device 510 is 2K, and display device 510 does not support theHDR (in case of an SDR) as illustrated in FIG. 23, the 2K and SDR outputsignal is output.

19. Operation Model of Playing Back HDR Signal and 4K Signal

FIG. 24 is a view illustrating an example of an operation model ofplaying back a 4K HDR signal, a 2K HDR signal and a 4K SDR signal in anext-generation Blu-ray playback device, and outputting playback signalsto an HDR supporting 4K TV, an HDR non-supporting 4K TV and an SDRsupporting 2K TV.

The Blu-ray playback device obtains static HDR meta data stored incontent management information, and dynamic HDR meta data stored in avideo encoded stream. By using these items of HDR meta data, the Blu-rayplayback device converts a video HDR signal into an SDR signal to outputaccording to characteristics of an output destination TV connectedaccording to HDMI, or outputs HDR meta data as a HDMI control signal.

Each process of converting an HDR signal into an SDR signal and aprocess of converting an HDR signal into a video signal of a luminancerange matching a display device can be selected from a plurality ofmethods and implemented. By storing HDR meta data matching theimplemented conversion process, in content management information or avideo encoded stream during creation of content, it is possible toenhance an effect of the conversion process. The content managementinformation or the encoded stream can store a plurality of items of HDRmeta data per converting method.

In addition, the Blu-ray playback device may include a plurality ofconversion processors such as option conversion module B or optionconversion module D, may include only one conversion processor by takinginto account a balance between device cost and performance or may notinclude a conversion processor. Similarly, an HDR supporting TV mayinclude a plurality of conversion processors, may include only oneconversion processor or may not include a conversion processor.

Further, similar to a user data storage SEI message illustrated in FIG.14 or 15, HDR meta data is stored in a predetermined container whichdefines a format and an operation during an input. Consequently, evenwhen a new conversion process is developed in future, new HDR meta datais defined and a display device which supports this new HDR meta data isconnected to a Blu-ray device which does not support the new HDR metadata, it is possible to output new HDR meta data from the Blu-rayplayback device to the display device. Further, the display device canperform a conversion process matching new HDR meta data. Consequently,when a new technique is developed, it is possible to support the newtechnique by a simple process of assigning an ID to new HDR meta data.Consequently, it is possible to enhance competitiveness of package mediastandards such as Blu-ray against applications such as OTT whosetechnical development is fast. In addition, the Blu-ray playback devicewhich supports new HDR meta data may perform the new conversion processon video data in the playback device, and output the processed videodata to the display device.

Further, which one of the Blu-ray playback device and a TV performs aconversion process is determined based on the methods illustrated inFIGS. 19 to 21. In addition, the playback device may down-convert a 4Ksignal into a 2K signal according to a resolution of the TV to output.

20. Method 1 for Storing HDR Meta Data

FIG. 25 is a view illustrating an example of a method for storing staticHDR meta data and two items of dynamic HDR meta data. As illustrated inFIG. 20, an extendable HDR method according to the present exemplaryembodiment, three items of (a) static HDR meta data, (b) dynamic HDRmeta data clip (dynamic HDR meta data) and (c) dynamic HDR meta data areused.

(a) Static HDR meta data is stored in a meta data storage area of eachstream (a playlist in case of a BDA (Blu-ray Disc Association)) definedby application standards of the BDA or the like or a distributionsystem. (b) A dynamic HDR meta data clip (dynamic HDR meta data) isstored in a secondary use TS stream defined by application standards ofthe BDA or the like or a distribution system. (c) Dynamic HDR meta datais stored as a SEI message included in a video stream such as HEVC.

By properly using these three items of data, it is possible to change acombination of items of meta data to use when a new HDR technique isintroduced. Consequently, it is possible to change conditions tointroduce a new HDR technique. For example, when an original HDRtechnique needs to be introduced as soon as possible without consideringcompatibility, it is possible to introduce the original HDR techniquewithout influencing application standards or a distribution system byusing only meta data (c). By contrast with this, when a new techniqueneeds to be defined by application standards or a distribution system byconsidering compatibility even though a time is taken more or less, itis possible to realize both of compatibility and timely introduction ofa new technique by using the items of meta data (a) and (b).

21. Method 2 for Storing HDR Meta Data

An example of how to use the three items of meta data (a) to (c)illustrated in FIG. 25 will be described in detail by using Blu-ray asan example.

First, a case where a proponent of a new HDR technique wishes earlyimplementation will be described. In this case, only meta data (c) isused. (1) The proponent discloses only an outline of the new HDRtechnique. (2) A test disk in which meta data of the new technique forchecking compatibility with an existing HDR (basic portion) Blu-rayplayback device is provided. (3) The BDA registers the new technique asa non-official option, does not test non-compatibility and takes noresponsibility. (4) The BDA takes no responsibility.

Next, a case where the proponent of the new HDR technique considerscompatibility to widely spread the new technique will be described. Inthis case, only the items of meta data (a) and (b) are used. (1) Theproponent discloses details of the technique. (2) A draft of aspecification for Blu-ray to adapt the technique to Blu-ray issubmitted. (3) A draft of a test specification for Blu-ray to adapt thetechnique to Blu-ray is submitted. (4) A test stream is provided. (5) Atest disk is provided. (6) A verifier is updated. (7) The BDA registersthe new technique as an official option, annexes the new technique towritten standards and tests compatibility at minimum. (8) The BDApermits an announcement that the new technique is adopted as an officialoption by the BDA.

[22. User Guidance Display Method 1] FIG. 26 is a view illustrating amethod for displaying a user guidance in a Blu-ray device which executesan HDR-SDR conversion process.

An algorithm of an HDR-SDR conversion process is not established, andtherefore it is difficult to accurately perform HDR-SDR conversion in acurrent situation. Further, it is also possible to implement a pluralityof algorithms of an HDR-SDR conversion process.

Hence, when a user inserts an HDR supporting disk into an HDR supportingBlu-ray device connected to an HDR non-supporting TV, it is necessary toappropriately guide users.

When the HDR supporting Blu-ray device connected to the HDRnon-supporting TV detects a start of an HDR-SDR conversion process, aguide message such as “The disk is an HDR non-supporting disk. Your TVis HDR non-supporting TV, and SDR video image converted from HDR intoSDR by the Blu-ray device is played back instead of HDR video image.” isdisplayed.

Thus, when the display device does not support a video output of aluminance range of the first video signal (HDR signal), the data outputdevice (Blu-ray device) outputs the second video signal (SDR signal)converted from a first luminance range into a second luminance range,and HDR control information to the display device, and causes thedisplay device to display something to the effect that the second videosignal converted from the first luminance range into the secondluminance range is displayed.

23. User Guidance Display Method 2

FIG. 27 is a view illustrating a method for displaying a user guidanceduring execution of a process of converting an HDR stored in a disk intoan SDR.

A message (menu) which needs to be displayed by a Blu-ray device when anHDR-SDR conversion process is performed is stored in an HDR disk or anon-volatile memory in the Blu-ray device. Consequently, the Blu-raydevice can display a message during execution of an HDR-SDR conversionprocess. In this case, for example, a message such as “The disk is anHDR supporting disk. Your TV is HDR non-supporting TV, and SDR videoimage converted from HDR into SDR by the Blu-ray device is played backinstead of HDR video image.” is displayed.

24. User Guidance Display Method 3

FIG. 28 is a view illustrating a method for displaying a user guidancemenu during execution of a process of converting an HDR stored in a diskinto an SDR.

By using a Blu-ray menu, the Blu-ray device can display a message suchas “The disk is HDR supporting disk. Your TV is HDR non-supporting TV,and SDR video image converted from HDR into SDR by the Blu-ray device isplayed back instead of HDR video image. Would you like to play back SDRvideo image?”. When a user pushes “Play back” button, the Blu-ray devicestarts displaying converted image. Further, when the user selects “Donot play back”, the Blu-ray device stops playback, and displays amessage which encourages the user to insert an HDR non-supportingBlu-ray disc.

Thus, when the display device does not support a video output of aluminance range of the first video signal (HDR signal), the data outputdevice (Blu-ray device) causes the display device to display a messagewhich encourages the user to select whether or not to display the secondvideo signal (SDR signal) converted from the first luminance range intothe second luminance range.

25. User Guidance Display Method 4

FIG. 29 is a view illustrating a method for displaying a user guidancemenu which enables selection of a processing method during execution ofa process of converting an HDR stored in a disk into an SDR.

The Blu-ray device displays something to the effect that meta data foran HDR-SDR conversion process is stored in Blu-ray when the meta data isstored in Blu-ray. When the user selects a specified converting method,the Blu-ray device displays a message indicating that more beautifulconversion is possible. That is, according to a Java (registeredtrademark) command in a disk, what HDR-SDR conversion process isimplemented in the Blu-ray device is determined. Consequently, theBlu-ray device can display a selection menu of an HDR-SDR conversionprocessing method, such as “The disk is HDR supporting disk. Your TV isHDR non-supporting TV, and SDR video image converted from HDR into SDRby the Blu-ray device is played back instead of HDR video image. Whichmethod do you choose? (Play back by process 1), (Play back by process 3)and (Do not play back)”. In addition, in this regard, process 1 andprocess 3 are different types of HDR-SDR conversion processes.

Thus, when the display device does not support a video output of aluminance range of the first video signal (HDR signal), the data outputdevice (Blu-ray device) causes the display device to display a messagewhich encourages the user to select one of a plurality of convertingmethods for converting the first luminance range into the secondluminance range.

26. User Guidance Display Method 5

In addition, it is also possible to display the same message bybroadcasting, too. For example, a TV or a playback device which does notsupport an HDR signal displays a message by using a data broadcastapplication that a broadcast program uses HDR signals and cannot beaccurately displayed when the program is viewed. Further, a TV or aplayback device which supports an HDR signal may not display thismessage. Furthermore, a tag value indicating a message attributeindicates that the message is a warning message for HDR signals. The TVor the playback device which supports HDR signals determines that it isnot necessary to display a message by referring to a tag value.

27. Method for Transmitting HDR Meta Data

For example, dynamic HDR meta data or static HDR meta data adopts a datastructure which can be transmitted according to HDMI. In this regard,depending on a specification or a version of a transmission protocolsuch as HDMI, whether or not it is possible to transmit HDR meta data tothe display device according to the transmission protocol is determined.

First, the method for transmitting dynamic HDR meta data will bedescribed.

For example, according to existing HDMI2.0, it is not possible totransmit dynamic HDR meta data which is variable in frame or sceneunits. Therefore, it is necessary to extend standards and newly define apacket for transmitting the dynamic HDR meta data. A version of thisextension standards is 2.1.

In this case, when the playback device such as an HDR supporting Blu-raydevice or a broadcast receiving device is connected with a displaydevice such as a TV via HDMI2.1, the playback device can transmitdynamic HDR meta data to the display device. However, when the playbackdevice and the display device are connected according to HDMI of anolder version than 2.1, the playback device cannot transmit the dynamicHDR meta data to the display device.

First, the playback device determines whether or not a HDMI versionwhich can establish connection with the display device supportstransmission of dynamic HDR meta data. When the version does not supporttransmission of dynamic HDR meta data, the playback device performs anHDR-SDR conversion process by using dynamic HDR meta data, and thenoutputs the converted signal to the display device according to HDMI.

Further, the playback device may operate also based on whether or notthe display device supports a conversion process performed by usingdynamic HDR meta data. That is, when the display device does not supporta conversion process, and even when the playback device can transmitdynamic HDR meta data according to a HDMI version, the playback devicemay perform a conversion process. Further, when the playback device doesnot support a conversion process performed by using dynamic HDR metadata, the playback device may not perform a conversion process and maynot transmit the dynamic HDR meta data to the display device, either.

FIG. 30 is a flowchart illustrating a method of the playback device fortransmitting dynamic HDR meta data. First, the playback devicedetermines whether or not the playback device and the display device areconnected according to HDMI2.0 or an older version than HDMI2.0 (S501).In other words, the playback device determines whether or not theplayback device and the display device can be connected according toHDMI2.1 which supports transmission of dynamic HDR meta data. Morespecifically, the playback device determines whether or not both of theplayback device and the display device support HDMI2.1.

When the playback device and the display device are connected accordingto HDMI2.0 or an older version than HDMI2.0 (Yes in S501), the playbackdevice performs a conversion process by using dynamic HDR meta data andtransmits converted image data to the display device according to HDMI(S502). The conversion process described herein is a process of changinga luminance range of image data, and is a process of converting an HDRinto an SDR to match a luminance range supported by the display deviceor a process of converting an HDR into an HDR signal of a narrowerluminance range.

Meanwhile, when the playback device and the display device are connectedaccording to HDMI2.1 or a newer version than HDMI2.1 (No in S501), theplayback device transmits image data for which a conversion process isnot yet performed, and dynamic HDR meta data to the display deviceaccording to HDMI by using different types of packets (S503).

Next, a method for transmitting static HDR meta data will be described.

It is possible to use Infoframe such as AVI (Auxiliary VideoInformation) Infoframe to transmit static HDR meta data according toHDMI. However, a maximum data size which can be stored in AVI Infoframeis 27 bytes according to HDMI2.0, and therefore data having a largersize than this maximum data size cannot be processed. Hence, when astatic HDR meta data size exceeds an upper limit value at which data canbe transmitted according to HDMI, the playback device transmits data forwhich a conversion process has been performed, to the display device.Alternatively, when a static HDR meta data size which can be transmitteddiffers depending on a HDMI version, the playback device determineswhether to transmit static HDR meta data to the display device based ona HDMI version for connecting the playback device and the displaydevice, and perform a conversion process in the playback device.

Further, the static HDR meta data may be classified into a requiredportion and an extension portion, and a size of the required portion maybe set to a size or less which can be transmitted according to aspecific version of a specific transmission protocol such as existingHDMI2.0. For example, the playback device may transmit only the requiredportion to the display device when using HDMI2.0, and may transmit therequired portion and the extension portion together when using HDMI2.1.Further, identification information indicating that static HDR meta dataincludes a necessary portion and an extension portion or indicating thatat least the required portion can be transmitted according to a specificversion such as HDMI2.0 may be stored in a database such as PlayList orPlayItem in a Blu-ray disc.

Alternatively, more simply, static HDR meta data may be set to a size orless which can be transmitted according to a lowest version such asHDMI2.0 which enables transmission of static HDR meta data. In addition,a syntax of static HDR meta data in a disk stored in managementinformation such as a playlist or video stream SEI, and a syntax ofstatic HDR meta data which is transmitted according to HDMI may bedifferent. When both of the syntaxes are different, the playback deviceconverts the static HDR meta data in the disk into the syntax of thestatic HDR meta data according to the transmission protocol to output.

In addition, content of Blu-ray has been described as an example.However, the same applies to meta data which is used for broadcasting orthe OTT.

FIG. 31 is a flowchart illustrating a method of the playback device fortransmitting static HDR meta data. First, the playback device determineswhether or not the playback device and the display device are connectedaccording to HDMI2.0 or an older version than HDMI2.0 (S511).

When the playback device and the display device are connected accordingto HDMI2.0 or an older version than HDMI2.0 (Yes in S511), the playbackdevice transmits only a required portion of static HDR meta data to thedisplay device according to HDMI (S512).

Meanwhile, when the playback device and the display device are connectedaccording to HDMI2.1 or a newer version than HDMI2.1 (No in S511), theplayback device transmits both of a required portion and an extensionportion of static HDR meta data to the display device according to HDMI(S513).

Thus, the playback device switches whether or not to transmit dynamicHDR meta data to the display device according to a HDMI version, yettransmits at least a required portion of static HDR meta data to thedisplay device at all times irrespectively of the HDMI version.

That is, the playback device transmits a video signal to the displaydevice. When a version of a transmission protocol which connects theplayback device and the display device is a first version (e.g.HDMI2.0), the playback device transmits, to the display device, firstmeta data (static HDR meta data) which is information which is commonlyused for a plurality of images included in continuous playback units ofthe video signal and relates to a luminance range of the video signal,without transmitting, to the display device, second meta data (dynamicHDR meta data) which is information which is commonly used for unitssubdivided compared to the continuous playback units of the video signaland relates to the luminance range of the video signal. Further, whenthe version of the transmission protocol is the second version (e.g.HDMI2.1), the playback device transmits both of the first meta data(static HDR meta data) and the second meta data (dynamic HDR meta data)to the display device.

Consequently, the playback device can transmit appropriate meta data tothe display device according to the version of the transmissionprotocol.

Further, when the version of the transmission protocol is the firstversion (e.g. HDMI2.0) (Yes in S501), the playback device performs aprocess of converting a luminance range of a video signal by using thesecond meta data (dynamic HDR meta data), and transmits the convertedvideo signal to the display device (S502).

Thus, when dynamic HDR meta data cannot be transmitted to the displaydevice and the display device cannot perform a conversion process, theplayback device can perform a conversion process.

Further, when the version of the transmission protocol is the secondversion (e.g. HDMI2.1) and the display device does not support aconversion process, the playback device performs a conversion process,transmits the converted video signal to the display device and does nottransmit the second meta data to the display device. Furthermore, whenthe version of the transmission protocol is the second version (e.g.HDMI2.1) and the display device supports a conversion process, theplayback device transmits a video signal and the second meta data to thedisplay device without performing a conversion process.

Consequently, one appropriate device of the playback device and thedisplay device can execute a conversion process.

Further, when the playback device does not support a conversion processof converting a luminance range of a video signal by using the secondmeta data (dynamic HDR meta data), the playback device transmits thevideo signal to the display device without performing the conversionprocess, and does not transmit the second meta data (dynamic HDR metadata) to the display device.

28. Adjustment of Luminance Value

How to use HDR meta data to faithfully reproduce an HDR signal andHDR-SDR conversion in the playback device have been described above.However, an HDR signal has a substantially high peak luminance than thatof a conventional SDR signal. Therefore, the playback device may controla peak luminance of a video image by taking into account performance ofa panel or a signal processing circuit of the display device such as aTV or an influence on a human body. In addition, the process describedbelow (playback method) may be performed by the playback device such asa Blu-ray device or may be performed by the display device such as a TV.In other words, the playback device described below only needs to have afunction of playing back video images, and includes the above-describedplayback device (e.g. Blu-ray device) and the display device (e.g. TV).

In this regard, even when an upper limit of a luminance value which canbe output from each pixel of a TV panel is 1000 nit, an area which canoutput a luminance of 1000 nit simultaneously is assumed to be limitedto 50% of a screen. In this case, even when 70% of an area of a screenis 1000 nit, a signal value of an HDR signal cannot be output as is.Hence, the playback device may control a luminance value of each pixelto play back an HDR signal based on following playback conditions.

First, a first method will be described. The playback device adjusts aluminance value such that an inter-screen luminance change amount atreference time interval T is threshold P or less. Reference timeinterval T described herein is, for example, an integer multiple of areciprocal of a video frame rate.

Threshold P is an absolute value of a luminance or a rate of a change ofa luminance value. This threshold P is determined based on an influencewhich a flash of an image has on a human body or following performanceof a TV panel for a change of a signal value.

Further, conditions may be set such that a number of pixels whoseintra-screen luminance value change amounts exceeds threshold P is apredetermined rate or less. Furthermore, the screen may be divided intoa plurality of areas, and the same or different conditions may be setper area.

Next, a second method will be described. The playback device adjusts aluminance value such that a number of pixels which have luminances ofreference luminance S or more or a rate that these pixels occupy intotal pixels in a screen is threshold Q or less.

Reference luminance S and threshold Q are determined based on aninfluence on a human body or an upper limit value of a voltage which issimultaneously applicable to each pixel of a TV panel.

Further, when parameters (threshold P, reference luminance S andthreshold Q) used for the first method and the second method are setbased on performance of a TV panel, values of the parameters can be setper TV.

A method for controlling a pixel value according to the first methodwill be described below. For example, a peak luminance of a plurality ofpixels configuring a frame at time t is assumed to be L1. When aluminance value of a pixel whose coordinate is (i,j) in a frame at timet+T is I(i,j), the playback device adjusts a luminance value for eachpixel whose absolute value of a difference between I(i,j) and L1 exceedsthreshold P such that the difference is threshold P or less. Thisprocess may be performed on an entire screen or may be performed perarea by dividing the screen to perform processes in parallel. Forexample, the playback device divides the screen in a horizontaldirection and a vertical direction, respectively, and adjusts aluminance value such that a change amount of a luminance in each area isthreshold P or less.

Further, a frame interval to display images on a TV panel is assumed tobe as reference time interval T. However, there is a case where, when aluminance value is adjusted based only on a luminance value of a lastframe, continuity of luminance values between frames is sometimes lost.Hence, a predetermined time constant may be set, and the playback devicemay determine a luminance value (above L1) by adding a weight to a peakluminance of each frame in a range of the set time constant. In thiscase, a time constant and a weighting coefficient are set in advancesuch that a change amount of a luminance value is threshold P or less.

Next, a method for controlling a pixel value according to the secondmethod will be described. This control method includes following twotypes of methods. The first method is a method for clipping a luminancevalue for each pixel whose luminance value exceeds a predeterminedvalue. For example, a luminance value of each pixel whose luminancevalue exceeds the predetermined value is adjusted to the predeterminedvalue.

The second method is a method for entirely lowering a luminance value ofeach pixel in the screen such that a relative luminance value ratebetween pixels is held as much as possible by, for example, setting Kneepoint instead of uniformly clipping each luminance value. Alternatively,a luminance value of a high luminance portion may be lowered while aluminance value of a low luminance portion is held.

For example, it is assumed that the number of pixels of a TV panel is 8mega pixels, and that a total sum of luminance values of all pixels in ascreen is limited to 8 mega×500 nit=4 giga nit or less. In this regard,it is assumed that a luminance value of an HDR signal of content is 400nit in area A (4 mega pixels) which is half of the screen, and is 1000nit in area B (4 mega pixels) which is the rest of the half. In thiscase, when each luminance value is uniformly clipped, all luminancevalues in area B are clipped to 600 nit. As a result, a total sum ofluminance values of all pixels is 4 mega×400+4 mega×600=4 giga nit andsatisfy the above limitation.

In addition, not only to play back an HDR signal but also to generate anHDR signal, a luminance value of each pixel in a frame of a video or astill image may be determined such that the conditions of the abovefirst method or second method are satisfied.

FIG. 32 is a flowchart of a method for controlling a luminance valueduring playback of an HDR signal. First, the playback device determineswhether or not an inter-screen luminance value change amount or anintra-screen luminance value satisfies playback conditions (S521). Morespecifically, as described above, the playback device determines whetheror not the inter-screen luminance value change amount is the thresholdor less or the intra-screen luminance value is the threshold or less.

When the inter-screen luminance value change amount or an intra-screenluminance value satisfies the playback conditions, i.e., when theinter-screen luminance change amount is the threshold or less or theintra-screen luminance value is the threshold or less (Yes in S521), theplayback device outputs a signal of the same luminance value as aluminance value of an input HDR signal (S522). That is, the playbackdevice outputs a luminance value of an HDR signal without adjusting theluminance value.

Meanwhile, when the inter-screen luminance value change amount or theintra-screen luminance value does not satisfy the playback conditions,i.e., when the inter-screen luminance change amount exceeds thethreshold or the intra-screen luminance value exceeds the threshold (Noin S521), the playback device adjusts a luminance value of each pixeland outputs an adjusted luminance value to satisfy the playbackconditions (S523). That is, the playback device adjusts the luminancevalue of each pixel such that the inter-screen luminance value changeamount is the threshold or less or the intra-screen luminance value isthe threshold or less.

As described above, the playback device according to the presentexemplary embodiment plays back video signals. A luminance of a videosignal is a first luminance value in a first luminance range whosemaximum luminance value is defined as a first maximum luminance valueexceeding 100 nit. That is, the video signal is an HDR signal.

As described above with reference to the first method, the playbackdevice determines whether or not an inter-screen luminance value changeamount of a video signal exceeds a predetermined first threshold (S521).For example, the playback device determines whether or not the luminancevalue change amount at a reference time interval which is an integermultiple of a reciprocal of a frame rate of the video signal exceeds thefirst threshold.

When it is determined that the luminance value change amount exceeds thefirst threshold (No in S521), the playback device performs an adjustmentprocess of lowering the luminance value of the video signal (S523). Morespecifically, for a pixel whose luminance value change amount exceedsthe first threshold, the playback device adjusts a luminance value ofthe pixel such that the luminance value change amount of the pixel isthe first threshold or less.

Consequently, when a luminance value of a video signal exceeds displaycapability of the display device, the playback device can generate avideo signal which the display device can appropriately display bylowering the luminance value of the video signal. Further, when a largechange amount of a luminance value of a video signal is likely tonegatively influence viewers, the playback device can reduce thenegative influence by lowering the luminance value of the video signal.

More specifically, in step S521, the playback device determines whetheror not a difference between a peak luminance of a first image includedin the video signal, and each of luminance values of a plurality ofpixels included in a second image in the video signal subsequent to thefirst image exceeds the first threshold may be determined. In step S523,for a pixel whose difference exceeds the first threshold, the playbackdevice adjusts a luminance value of the pixel such that the differenceof the pixel is the first threshold or less.

Alternatively, in step S521, the playback device determines whether ornot a rate of pixels whose luminance value change amounts exceed thefirst threshold with respect to a plurality of pixels included in animage included in the video signal exceeds a second threshold. In stepS523, when the rate exceeds the second threshold, the playback deviceadjusts luminance values of the plurality of pixels such that the rateis the second threshold or less.

Further, in step S521, for each of a plurality of areas obtained bydividing the screen, the playback device determines whether or not aninter-screen luminance value change amount of each area exceeds thefirst threshold. In step S523, the playback device performs anadjustment process of lowering a luminance value of an area for which itis determined that the luminance value change amount exceeds the firstthreshold.

Alternatively, as described above with reference to the second method,the playback device determines whether or not a luminance value of animage included in a video signal exceeds the predetermined firstthreshold (S521). When it is determined that the luminance value of eachpixel exceeds the first threshold (No in S521), the playback deviceperforms an adjustment process of lowering the luminance value of theimage (S523).

Consequently, when a luminance value of a video signal exceeds displaycapability of the display device, the playback device can generate avideo signal which the display device can appropriately display bylowering the luminance value of the video signal. Further, when a highluminance value of a video signal is likely to negatively influenceviewers, the playback device can reduce the negative influence bylowering the luminance value of the video signal.

More specifically, in step S521, the playback device determines thenumber of pixels whose luminance values exceed the first threshold amonga plurality of pixels included in an image. In step S523, when thenumber of pixels whose luminance values exceed the first thresholdexceeds the third threshold, the playback device lowers the luminancevalue of the image such that the number of pixels whose luminance valuesexceed the first threshold is a third threshold or less.

Alternatively, in step S521, the playback device determines a rate ofpixels whose luminance values exceed the first threshold with respect toa plurality of pixels included in the image. In step S523, when the rateexceeds the third threshold, the playback device lowers the luminancevalue of the image such that the rate is the third threshold or less.

Further, the first threshold, the second threshold and the thirdthreshold are values calculated based on an upper limit value of avoltage which is simultaneously applicable to a plurality of pixels in adisplay device which displays video signals.

29. Method for Arranging Meta Data

A method for arranging static HDR meta data and dynamic HDR meta data ina video stream will be described below.

Static HDR meta data may be stored in a head access unit in a decodingorder in random access units such as GOP to store the static HDR metadata in a video stream by using SEI. In this case, a NAL unit includingSEI is arranged prior to a NAL unit in which a video encoded data isstored in the decoding order.

Further, the same meta data is used as these two items of dynamic HDRmeta data to store the dynamic HDR meta data in both of managementinformation such as a playlist, and a video stream.

Furthermore, dynamic HDR meta data can be switched in random accessunits and is fixed in the random access units. For example, SEI in whichdynamic HDR meta data is stored is stored in a head access unit in therandom access units. Decoding starts from a head of the random accessunits to start playback from a middle of a stream. Further, duringspecial playback such as high-speed playback of playing back onlypicture I and picture P, a head access unit in the random access unitsis decoded at all times. Hence, by storing HDR meta data in a headaccess unit in the random access units, the playback device can obtainHDR meta data at all times.

In a stream according to MPEG-4 AVC or HEVC, only a head access unit inthe decoding order in the random access units includes a SequenceParameter Set (SPS) which is initialization information during decoding.It is possible to use this SPS as information indicating start of therandom access units.

Further, static HDR meta data and dynamic HDR meta data may be stored indifferent SEI messages. Both of the SEI messages are identified based onidentification information included in a type of the SEI message or thepayload of the SEI message. When, for example, transmitting only staticHDR meta data according to HDMI, the playback device can extract only aSEI message including the static HDR meta data, and transmit meta dataincluded in a payload as it is according to HDMI. Consequently, theplayback device does not need to perform a process of analyzing apayload of the SEI message, and obtaining static HDR meta data.

30. Dual Disk Playback Operation 1

An operation of playing back an HDR disk in which only HDR signals arestored has been described above.

Next, multiplexed data stored in a dual disk in which both of HDRsignals and SDR signals are stored will be described with reference toFIG. 33. FIG. 33 is a view for explaining multiplexed data stored in adual disk.

As illustrated in FIG. 33, HDR signals and SDR signals are stored asdifferent multiplexed streams in the dual disk. For example, items ofdata of a plurality of media such as a video, an audio, a caption andgraphics are stored as one multiplexed stream in an optical disk such asBlu-ray according to a MPEG-2 TS-based multiplexing method called M2TS.A reference is made to these multiplexed streams from playback controlmeta data such as a playlist. During playback, a player analyzes metadata to select a multiplexed stream to play back or individual languagedata stored in the multiplexed stream. This example is a case where HDRand SDR playlists are individually stored, and the respective playlistsrefer to HDR signals or SDR signals. Further, identification informationindicating that both of HDR signals and SDR signals are stored may beadditionally indicated.

It is also possible to multiplex both of HDR signals and SDR signals inthe same multiplexed stream. However, it is necessary to performmultiplexing to satisfy a buffer model such as T-STD (System TargetDecoder) defined according to MPEG-2 TS. Particularly, it is difficultto multiplex two videos of high bit rates within a range of apredetermined data reading rate. Hence, it is desirable to demultiplexmultiplexed streams.

Data such as an audio, a caption or graphics needs to be stored for eachmultiplexed stream, and a data amount increases compared to a case wheredata is multiplexed into one video stream. In this regard, it ispossible to reduce an increase in a data amount by reducing a video dataamount by using a video encoding method of a high compressibility. Forexample, by changing MPEG-4 AVC which is conventionally used for Blu-rayto HEVC (High Efficiency Video Coding), the compressibility is expectedto improve 1.6 to 2 times. Further, by storing a combination of a 2K HDRand a 2K SDR or a combination of a 4K SDR and a 2K HDR, i.e., by storingtwo 2Ks or a combination of 2K and 4K in a dual disk, storing two 4Ksmay be banned to permit only a combination which can be stored in anoptical disk.

31. Conclusion

A Blu-ray device which plays back a 4K supporting BD or an HDRsupporting BD needs to support four TVs of a 2K_SDR supporting TV, a 2KHDR supporting TV, a 4K_SDR supporting TV and a 4K HDR supporting TV.More specifically, the Blu-ray device needs to support three pairs ofHDMI/HDCP (High-bandwidth Digital Content Protection) standards(HDMI1.4/HDCP1.4, HDMI2.0/HDCP2.1 and HDMI2.1/HDCP2.2).

Further, when playing back four types of Blu-ray discs (a 2K_SDRsupporting BD, a 2K HDR supporting BD, a 4K_SDR supporting BD and a 4KHDR supporting BD), the Blu-ray device needs to select an appropriateprocess and HDMI/HDCP per BD (content) and per connected display device(TV). Furthermore, when graphics are synthesized with a video, too, itis necessary to change a process according to a BD type and a connecteddisplay device (TV) type.

Hence, an internal process in the Blu-ray device becomes very complex.In the third exemplary embodiment, various methods for relativelysimplifying a process in the Blu-ray device have been described.

[1] It is necessary to convert an HDR into an SDR to display an HDRsignal on an HDR non-supporting TV. By contrast with this, in the thirdexemplary embodiment, a configuration of a BD which is a dual streamsdisk has been proposed to make this conversion optional in a Blu-raydevice.

[2] Further, in the third exemplary embodiment, a graphic stream islimited, and types of combinations of video streams and graphic streamsare reduced.

[3] In the third exemplary embodiment, a dual streams disk and a graphicstream are limited to substantially reduce a number of combinations of acomplex process in a Blu-ray device.

[4] In the third exemplary embodiment, an internal process and a HDMIprocess which do not produce a contradiction for a process of a dualstreams disk even when pseudo HDR conversion is introduced have beendescribed.

According to a converting method according to the present disclosure,“HDR pseudo HDR conversion process” of converting an HDR video image tokeep a gradation of an area exceeding 100 nit to some degree, convertingthe HDR video image into a pseudo HDR video image close to the originalHDR and enabling the SDR TV to display the HDR video image is realizedto display an HDR video image on an SDR TV instead of converting an HDRvideo image into an SDR video image of 100 nit or less by using a peakluminance of the SDR TV which is displayed and exceeds 100 nit(generally, 200 nit or more).

Further, according to the converting method, the converting method of“HDR pseudo HDR conversion process” may be switched according to displaycharacteristics (a maximum luminance, input/output characteristics and adisplay mode) of the SDR TV.

A method for obtaining display characteristics information includes (1)automatically obtaining the display characteristics information via HDMI(registered trademark) or a network, (2) generating the displaycharacteristics information by having a user input information such as amanufacturer name or a model and (3) obtaining the displaycharacteristics information from a cloud or the like by usinginformation of the manufacturer name or the model.

Further, a timing to obtain the display characteristics information ofconverting device 100 includes (1) obtaining the display characteristicsinformation immediately before pseudo HDR conversion, and (2) obtainingwhen connection with display device 200 (e.g. SDR TV) is established forthe first time (when connection is established).

Furthermore, as for the converting method, the converting method may beswitched according to HDR video image luminance information (CAL(Content Average Luminance) and CPL (Content Peak Luminance)).

For example, a method for obtaining the HDR video image luminanceinformation of converting device 100 includes (1) obtaining the HDRvideo image luminance information as meta information accompanying anHDR video image, (2) obtaining the HDR video image luminance informationby having the user input title information of content and (3) obtainingthe HDR video image luminance information by using input informationinput by the user, from a cloud or the like.

Further, details of the converting method include (1) performingconversion such that a luminance does not exceed a DPL (Display PeakLuminance), (2) performing conversion such that CPL is DPL, (3) notchanging a CAL and a luminance around the CAL, (4) performing conversionby using a natural logarithm and (5) performing a clip process by usingthe DPL.

Furthermore, according to the converting method, it is also possible totransmit display settings such as a display mode and a display parameterof the SDR TV to display device 200 to switch to enhance a pseudo HDReffect. For example, a message which encourages the user to make thedisplay settings may be displayed on a screen.

32. Necessity 1 of Pseudo HDR

Next, the necessity of a pseudo HDR will be described with reference toFIGS. 34A to 34C.

FIG. 34A is a view illustrating an example of a display process ofconverting an HDR signal in an HDR TV and displaying an HDR.

As illustrated in FIG. 34A, when an HDR video image is displayed, andeven when the display device is an HDR TV, it is not possible to displaya maximum value of an HDR luminance range (peak luminance (HPL (HDR PeakLuminance): e.g. 1500 nit)) in some cases. In this case, luminanceconversion for adjusting a linear signal which is inversely quantized byusing an HDR EOTF, to a maximum value of a luminance range of thedisplay device (peak luminance (DPL (Display Peak Luminance): e.g. 750nit)) is performed. Further, by inputting to the display device a videosignal obtained by performing the luminance conversion, it is possibleto display an HDR video image which has been adjusted to the luminancerange of the maximum value which is a limit of the display device.

FIG. 34B is a view illustrating an example of a display process ofdisplaying an HDR by using an HDR supporting playback device and an SDRTV.

As illustrated in FIG. 34B, when an HDR video image is displayed, andwhen the display device is an SDR TV, that a maximum value (peakluminance (DPL: e.g., 300 nit)) of a luminance range of the SDR TV whichdisplays the HDR video image exceeds 100 nit is used. In “HDR→pseudo HDRconversion process” in an HDR supporting playback device (Blu-raydevice) in FIG. 34B, “HDR EOTF conversion” performed in an HDR TV and“luminance conversion” performed by using a DPL (e.g.: 300 nit) which isthe maximum value of the luminance range of the SDR TV are performed. Inthis case, when it is possible to directly input a signal obtained byperforming “luminance conversion” to the “display device” which is theSDR TV, it is possible to realize the same effect as that of the HDR TVeven by using the SDR TV.

However, the SDR TV does not have means for receiving a direct input ofsuch a signal from an outside, and therefore cannot realize the sameeffect as that of the HDR TV.

FIG. 34C is a view illustrating an example of a display process ofdisplaying an HDR by using an HDR supporting playback device and an SDRTV which are connected with each other via a standard interface.

As illustrated in FIG. 34C, it is generally necessary to input a signalfor providing the effect in FIG. 34B, to the SDR TV by using an inputinterface (HDMI (registered trademark)) of the SDR TV. In the SDR TV,the signal input via the input interface passes in order of “SDR EOTFconversion”, “luminance conversion of each mode” and the “displaydevice”, and displays a video image matching a luminance range of amaximum value of the display device. Hence, an HDR supporting Blu-raydevice generates a signal (pseudo HDR signal) which can cancel “SDR EOTFconversion” and “luminance conversion of each mode” which the signalpasses immediately after the input interface of the SDR TV. That is, byperforming “luminance inverse conversion of each mode” and “SDR inverseEOTF conversion” immediately after “HDR EOTF conversion” and “luminanceconversion” performed by using a peak luminance (DPL) of the SDR TV, theHDR supporting Blu-ray device can realize in a pseudo manner the sameeffect as that obtained when a signal obtained immediately after“luminance conversion” is input to the “display device” (a broken linearrow in FIG. 34C).

33. Necessity 2 of Pseudo HDR

An input signal of a normal SDR TV is 100 nit yet has capability ofexpressing video images of 200 nit or more according to viewingenvironment (a dark room: a cinema mode, and a bright room: a dynamicmode). However, a luminance upper limit of an input signal to the SDR TVis determined as 100 nit, and therefore it has not been possible todirectly use this capability.

When the SDR TV displays HDR video images, that a peak luminance of theSDR TV which displays the HDR video images exceeds 100 nit (generally200 nit or more) is used. Instead of converting the HDR video imagesinto SDR video images of 100 nit or less, “HDR→pseudo HDR conversionprocess” is performed to keep a gradation of a luminance range exceeding100 nit to some degree. Consequently, the SDR TV can display pseudo HDRvideo images close to the original HDR.

When this “HDR→pseudo HDR conversion process” technique is applied toBlu-ray, as illustrated in FIG. 35, only HDR signals are stored in anHDR disk. When the SDR TV is connected to a Blu-ray device, the Blu-raydevice performs “HDR pseudo HDR conversion process”, converts an HDRsignal into a pseudo HDR signal and outputs the pseudo HDR signal to theSDR TV. Consequently, by converting the received pseudo HDR signal intoa luminance value, the SDR TV can display video images having a pseudoHDR effect. Thus, even when there is no HDR supporting TV, if an HDRsupporting BD and an HDR supporting Blu-ray device are prepared, even anSDR TV can display pseudo HDR video images having higher quality thanthat of SDR video images.

Hence, it has been thought that an HDR supporting TV is necessary toview HDR video images. However, an existing SDR TV can display pseudoHDR video images which realize an HDR effect. Consequently, it can beexpected that HDR-supporting Blu-ray spreads.

34. Effect and Others

By performing HDR-pseudo HDR conversion process on an HDR signaltransmitted by way of broadcasting, a package medium such as Blu-ray orInternet distribution such as the OTT, an HDR signal is converted into apseudo HDR signal. Consequently, an existing SDR TV can display the HDRsignal as a pseudo HDR video image.

35. EOTF

Hereinafter, the EOTF will be described with reference to FIGS. 36A and36B.

FIG. 36A is a view illustrating an example of the EOTF (Electro-OpticalTransfer Function) which supports the HDR and the SDR, respectively.

The EOTF is a generally called gamma curve, indicates eachcorrespondence between a code value and a luminance value and convertsthe code value into a luminance value. That is, the EOTF is associationinformation indicating a correspondence relationship between a pluralityof code values and luminance values.

Further, FIG. 36B is a view illustrating an example of an inverse EOTFwhich supports the HDR and the SDR, respectively.

The inverse EOTF indicates each correspondence between a luminance valueand a code value, and quantizes a luminance value contrary to the EOTFand converts the luminance value into a code value. That is, the inverseEOTF is association information indicating a correspondence relationshipbetween luminance value and a plurality of code values. When, forexample, a luminance value of an HDR supporting video image is expressedby a 10-bit code value of a gradation, a luminance value of an HDRluminance range up to 10,000 nit is quantized and mapped on 1024 integervalues of 0 to 1023. That is, the luminance value of the luminance rangeup to 10,000 nit (a luminance value of an HDR supporting video image) isquantized based on the inverse EOTF and thereby is converted into an HDRsignal of the 10-bit code value. An HDR supporting EOTF (referred to asa “HDR EOTF” below) or an HDR supporting inverse EOTF (referred to as a“HDR inverse EOTF” below) can express a higher luminance value than thatof an SDR supporting EOTF (referred to as a “SDR EOTF” below) or an SDRsupporting inverse EOTF (referred to as a “SDR inverse EOTF” below). Forexample, in FIGS. 36A and 36B, a maximum value of a luminance (peakluminance) is 10,000 nit. That is, an HDR luminance range includes anentire SDR luminance range, and an HDR peak luminance is higher than anSDR peak luminance. An HDR luminance range is a luminance range obtainedby expanding a maximum value from 100 nit which is a maximum value ofthe SDR luminance range to 10,000 nit.

For example, examples of the HDR EOTF and the HDR inverse EOTF includeSMPTE 2084 standardized by Society of Motion Picture & TelevisionEngineers (SMPTE).

In addition, in the following description, a luminance range from 0 nitto 100 nit which is a peak luminance illustrated in FIGS. 36A and 36Bwill be described as a first luminance range in some cases. Similarly, aluminance range from 0 nit to 10,000 nit which is a peak luminanceillustrated in FIGS. 36A and 36B will be described as a second luminancerange in some cases.

36. Converting Device and Display Device

FIG. 37 is a block diagram illustrating a configuration of theconverting device and the display device according to the exemplaryembodiment. FIG. 38 is a flowchart illustrating a converting method anda display method performed by the converting device and the displaydevice according to the exemplary embodiment.

As illustrated in FIG. 37, converting device 100 includes HDR EOTFconverter 101, luminance converter 102, luminance inverse converter 103and SDR inverse EOTF converter 104. Further, display device 200 includesdisplay setting unit 201, SDR EOTF converter 202, luminance converter203 and display 204.

Each component of converting device 100 and display device 200 will bedescribed in detail during description of the converting method and thedisplay method.

37. Converting Method and Display Method

The converting method performed by converting device 100 will bedescribed with reference to FIG. 38. In addition, the converting methodincludes step S101 to step S104 described below.

First, HDR EOTF converter 101 of converting device 100 obtains an HDRvideo image for which HDR inverse EOTF conversion has been performed.HDR EOTF converter 101 of converting device 100 performs HDR EOTFconversion on an HDR signal of the obtained HDR video image (S101).Thus, HDR EOTF converter 101 converts the obtained HDR signal into alinear signal indicating a luminance value. The HDR EOTF is, forexample, SMPTE 2084.

Next, luminance converter 102 of converting device 100 performs firstluminance conversion of converting the linear signal converted by HDREOTF converter 101 by using display characteristics information andcontent luminance information (S102). According to the first luminanceconversion, a luminance value corresponding to an HDR luminance range(referred to as a “HDR luminance value” below) is converted into aluminance value corresponding to a display luminance range (referred toas a “display luminance value” below). Details will be described below.

In view of the above, HDR EOTF converter 101 functions as an obtainingunit which obtains an HDR signal as a first luminance signal indicatinga code value obtained by quantizing the luminance value of a videoimage. Further, HDR EOTF converter 101 and luminance converter 102function as converters which determine the code value indicated by theHDR signal obtained by the obtaining unit, based on a display (displaydevice 200) luminance range, and converts the code value into a displayluminance value corresponding to the display luminance range which is amaximum value (DPL) which is smaller than a maximum value (HPL) of theHDR luminance range and is larger than 100 nit.

More specifically, in step S101, HDR EOTF converter 101 determines forthe HDR code value which is a first code value indicated by the obtainedHDR signal an HDR luminance value associated with an HDR code value bythe HDR EOTF by using the obtained HDR signal and the HDR EOTF. Inaddition, the HDR signal indicates the HDR code value obtained byquantizing video (content) luminance value by using the HDR inverse EOTFof associating luminance values of the HDR luminance range and aplurality of HDR code values.

Further, in step S102, luminance converter 102 determines for the HDRluminance value determined in step S101 a display luminance value whichis associated in advance with the HDR luminance value and corresponds tothe display luminance range, and performs first luminance conversion ofconverting the HDR luminance value corresponding to the HDR luminancerange into a display luminance value corresponding to the displayluminance range.

Furthermore, before step S102, converting device 100 obtains contentluminance information including at least one of a luminance maximumvalue (CPL: Content Peak luminance) of the video image (content) andaverage luminance value (CAL: Content Average luminance) of a videoimage, as information related to an HDR signal. The CPL (first maximumluminance value) is, for example, a maximum value among luminance valuesof a plurality of images configuring an HDR video image. Further, theCAL is, for example, an average luminance value which is an average ofluminance values of a plurality of images configuring an HDR videoimage.

Furthermore, before step S102, converting device 100 obtains displaycharacteristics information of display device 200 from display device200. In addition, the display characteristics information is informationindicating a maximum value (DPL) of a luminance which can be displayedby display device 200, a display mode (described below) of displaydevice 200 and display characteristics of display device 200 such asinput/output characteristics (an EOTF supported by the display device).

Further, converting device 100 may transmit recommended display settinginformation (which will be described below and also referred to as“setting information” below) to display device 200.

Next, luminance inverse converter 103 of converting device 100 performsluminance inverse conversion matching a display mode of display device200. Consequently, luminance inverse converter 103 performs secondluminance conversion of converting a luminance value corresponding tothe display luminance range into a luminance value corresponding to anSDR luminance range (0 to 100 [nit]) (S103). Details will be describedbelow. That is, luminance inverse converter 103 determines for thedisplay luminance value obtained in step S102 an SDR luminance valuewhich is a luminance value (referred to as a “SDR luminance value”below) associated in advance with the display luminance value andcorresponding to an SDR as a third luminance value corresponding to anSDR luminance range whose maximum value is 100 nit, and performs secondluminance conversion of converting the display luminance valuecorresponding to the display luminance range into the SDR luminancevalue corresponding to the SDR luminance range.

Further, SDR inverse EOTF converter 104 of converting device 100generates a pseudo HDR video image by performing SDR inverse EOTFconversion (S104). That is, SDR inverse EOTF converter 104 quantizes thedetermined SDR luminance value by using an inverse EOTF (Electro-OpticalTransfer Function) of an SDR (Standard Dynamic Range) which is thirdassociation information which associates luminance values of an HDRluminance range and a plurality of third code values, determines a thirdcode value obtained by the quantization, converts the SDR luminancevalue corresponding to the SDR luminance range into an SDR signals asthe third luminance signal indicating the third code value and therebygenerates a pseudo HDR signal. In addition, the third code value is acode value supporting the SDR, and will be referred to as a “SDR codevalue” below. That is, an SDR signal is expressed by an SDR code valueobtained by quantizing a luminance value of a video image by using anSDR inverse EOTF of associating luminance values of an SDR luminancerange and a plurality of SDR code values. Further, converting device 100outputs a pseudo HDR signal (SDR signal) generated in step S104 todisplay device 200.

Converting device 100 generates an SDR luminance value corresponding toa pseudo HDR by performing first luminance conversion and secondluminance conversion on an HDR luminance value obtained by inverselyquantizing an HDR signal, and generates an SDR signal corresponding tothe pseudo HDR by quantizing the SDR luminance value by using an EOTF.In addition, the SDR luminance value is a numerical value in a luminancerange of 0 to 100 nit corresponding to the SDR. However, the SDRluminance value is converted based on the display luminance range, andtherefore takes a numerical value which is obtained by performingluminance conversion on an HDR luminance value by using an HDR EOTF andan SDR EOTF and which is different from the luminance value in theluminance range of 0 to 100 nit corresponding to the SDR.

Next, the display method performed by display device 200 will bedescribed with reference to FIG. 38. In addition, the display methodincludes step S105 to step S108 described below.

First, display setting unit 201 of display device 200 sets displaysettings of display device 200 by using setting information obtainedfrom converting device 100 (S105). In this regard, display device 200 isan SDR TV. The setting information is information indicating displaysettings which is recommended for the display device, and is informationindicating how an EOTF is performed on a pseudo HDR video image and whatsettings can display beautiful video images (i.e., information forswitching the display settings of display device 200 to optimal displaysettings). The setting information includes, for example, gamma curvecharacteristics during an output of the display device, a display modesuch as a living mode (normal mode) or a dynamic mode, or a numericalvalue of a backlight (brightness). Further, display device 200 (alsoreferred to as a “SDR display” below) may display a message whichencourages the user to change the display settings of display device 200by a manual operation. Details will be described below.

In addition, before step S105, display device 200 obtains an SDR signal(pseudo HDR signal), and setting information indicating display settingswhich are recommended for display device 200 to display video images.

Further, display device 200 may obtain the SDR signal (pseudo HDRsignal) before step S106, and may obtain the SDR signal after step S105.

Next, SDR EOTF converter 202 of display device 200 performs SDR EOTFconversion on the obtained pseudo HDR signal (S106). That is, SDR EOTFconverter 202 inversely quantizes the SDR signal (pseudo HDR signal) byusing an SDR EOTF. Thus, SDR EOTF converter 202 converts an SDR codevalue indicated by an SDR signal into the SDR luminance value.

Further, luminance converter 203 of display device 200 performsluminance conversion according to the display mode set to display device200. Consequently, luminance converter 203 performs third luminanceconversion of converting an SDR luminance value corresponding to an SDRluminance range (0 to 100 [nit]) into a display luminance valuecorresponding to the display luminance range (0 to DPL [nit]) (S107).Details will be described below.

In view of the above, in step S106 and step S107, display device 200converts a third code value indicated by the obtained SDR signal (pseudoHDR signal) into a display luminance value corresponding to the displayluminance range (0 to DPL [nit]) by using the setting informationobtained in step S105.

More specifically, the SDR signal (pseudo HDR signal) is converted intothe display luminance value by, in step S106, determining for the SDRcode value indicated by the obtained SDR signal an SDR luminance valueassociated with the SDR code value by an SDR EOTF by using the EOTF ofassociating the luminance values in the SDR luminance range and aplurality of third code values.

Further, in step S107, an SDR signal is converted into a displayluminance value by, in step S107, determining a display luminance valuewhich is associated in advance with the determined SDR luminance valueand corresponds to the display luminance range, and performing thirdluminance conversion of converting the SDR luminance value correspondingto the SDR luminance range into a display luminance value correspondingto the display luminance range.

Finally, display 204 of display device 200 displays pseudo HDR videoimages on display device 200 based on the converted display luminancevalue (S108).

38. First Luminance Conversion

Next, details of the first luminance conversion (HPL DPL) in step S102will be described with reference to FIG. 39A. FIG. 39A is a view forexplaining an example of the first luminance conversion.

Luminance converter 102 of converting device 100 performs the firstluminance conversion of converting the linear signal (HDR luminancevalue) obtained in step S101 by using display characteristicsinformation and content luminance information of HDR video images.According to the first luminance conversion, an HDR luminance value(input luminance value) is converted into a display luminance value(output luminance value) which does not exceed a display peak luminance(DPL). The DPL is determined by using a maximum luminance and a displaymode of an SDR display which are the display characteristicsinformation. The display mode is, for example, mode information such asa theater mode of displaying video images darkly on the SDR display, anda dynamic mode of displaying video images brightly. When, for example,the maximum luminance of the SDR display is 1,500 nit and the displaymode is a mode providing brightness of 50% of the maximum luminance, theDPL is 750 nit. In this regard, the DPL (second maximum luminance value)is a luminance maximum value which can be displayed by a display modecurrently set to the SDR display. That is, according to the firstluminance conversion, the DPL which is the second maximum luminancevalue is determined by using display characteristics information whichis information indicating display characteristics of the SDR display.

Further, according to the first luminance conversion, a CAL and a CPL ofcontent luminance information are used, each luminance value equal to orless than the CAL is regarded as the same before and after conversion,and only each luminance value equal to or more than the CPL is changed.That is, as illustrated in FIG. 39A, according to the first luminanceconversion, when the HDR luminance value is the CAL or less, the HDRluminance value is not converted, the HDR luminance value is determinedas a display luminance value. Further, when the HDR luminance value isthe CPL or more, the DPL which is the second maximum luminance value isdetermined as a display luminance value.

Furthermore, according to the first luminance conversion, a peakluminance (CPL) of an HDR video image of luminance information is used,and the DPL is determined as a display luminance value when the HDRluminance value is the CPL.

In addition, according to the first luminance conversion, as illustratedin FIG. 39B, the linear signal (HDR luminance value) obtained in stepS101 may be converted to clip to a value which does not exceed the DPL.By performing such luminance conversion, it is possible to simplify aprocess in converting device 100, make converting device 100 smaller,reduce power of converting device 100 and increase a processing speed ofconverting device 100. In addition, FIG. 39B is a view for explaininganother example of the first luminance conversion.

39-1. Second Luminance Conversion

Next, details of the second luminance conversion (DPL→100 [nit]) in stepS103 will be described with reference to FIG. 40. FIG. 40 is a view forexplaining the second luminance conversion.

Luminance inverse converter 103 of converting device 100 performsluminance inverse conversion corresponding to a display mode, on thedisplay luminance value of the display luminance range (0 to DPL [nit])converted by the first luminance conversion in step S102. The luminanceinverse conversion is a process of making it possible to obtain thedisplay luminance value of the display luminance range (0 to DPL [nit])after the process in step S102 when the SDR display performs luminanceconversion process (step S107) corresponding to the display mode. Thatis, the second luminance conversion is luminance inverse conversion ofthe third luminance conversion.

As a result of the above process, according to the second luminanceconversion, the display luminance value (input luminance value) of thedisplay luminance range is converted into an SDR luminance value (outputluminance value of the SDR luminance range.

According to the second luminance conversion, a converting method isswitched according to a display mode of the SDR display. When, forexample, the display mode of the SDR display is the normal mode, aluminance is converted into a direct proportional value which isdirectly proportional to a display luminance value. Further, accordingto the second luminance conversion, in a case where the display mode ofthe SDR display is the dynamic mode which makes high luminance pixelsbrighter and makes low luminance pixels darker than those of the normalmode, an inverse function of the second luminance conversion is used toconvert an SDR luminance value of each low luminance pixel into a valuehigher than the direct proportional value which is directly proportionalto the display luminance value, and convert an SDR luminance value ofeach high luminance pixel into a value lower than the directproportional value which is directly proportional to the displayluminance value. That is, according to the second luminance conversion,for the display luminance value determined in step S102, a luminancevalue associated with the display luminance value is determined as anSDR luminance value by using luminance association informationcorresponding to display characteristics information which isinformation indicating display characteristics of the SDR display, andluminance conversion process is switched according to the displaycharacteristics information. In this regard, the luminance associationinformation corresponding to the display characteristics information isinformation which is defined per display parameter (display mode) of theSDR display as illustrated in, for example, FIG. 40 and which associatesa display luminance value (input luminance value) and an SDR luminancevalue (output luminance value).

39-2. Third Luminance Conversion

Next, details of the third luminance conversion (100→DPL [nit]) in stepS107 will be described with reference to FIG. 41. FIG. 41 is a view forexplaining the third luminance conversion.

Luminance converter 203 of display device 200 converts an SDR luminancevalue of an SDR luminance range (0 to 100 [nit]) into (0 to DPL [nit])according to the display mode set in step S105. This process isperformed to realize an inverse function of luminance inverse conversionof each mode in step S103.

According to the third luminance conversion, a converting method isswitched according to a display mode of the SDR display. When, forexample, the display mode of the SDR display is the normal mode (i.e., aset display parameter is a parameter supporting the normal mode),luminance conversion is performed to convert the display luminance valueinto a direct proportional value which is directly proportional to theSDR luminance value. Further, according to the third luminanceconversion, in a case where the display mode of the SDR display is thedynamic mode which makes high luminance pixels brighter and makes lowluminance pixels darker than those of the normal mode, luminanceconversion is performed to convert a display luminance value of each lowluminance pixel into a value lower than the direct proportional valuewhich is directly proportional to the SDR luminance value, and convert adisplay luminance value of each high luminance pixel into a value higherthan the direct proportional value which is directly proportional to theSDR luminance value. That is, according to the third luminanceconversion, for the SDR luminance value determined in step S106, aluminance value associated in advance with the SDR luminance value isdetermined as a display luminance value by using luminance associationinformation corresponding to a display parameter which indicates displaysettings of the SDR display, and luminance conversion process isswitched according to the display parameter. In this regard, theluminance association information corresponding to the display parameteris information which is defined per display parameter (display mode) ofthe SDR display as illustrated in, for example, FIG. 41 and whichassociates an SDR luminance value (input luminance value) and a displayluminance value (output luminance value).

40. Display Settings

Next, details of the display settings in step S105 will be describedwith reference to FIG. 42. FIG. 42 is a flowchart illustrating detailedprocess of the display settings.

Display setting unit 201 of the SDR display performs a following processin step S201 to step S208 in step S105.

First, display setting unit 201 determines whether or not an EOTF (SDRdisplay EOTF) set to the SDR display matches an EOTF assumed duringgeneration of a pseudo HDR video image (SDR signal) by using settinginformation (S201).

When determining that the EOTF set to the SDR display is different fromthe EOTF indicated by the setting information (the EOTF matching thepseudo HDR video image) (Yes in S201), display setting unit 201determines whether or not a system side can switch the SDR display EOTF(S202).

When determining that the system side can switch the SDR display EOTF,display setting unit 201 switches the SDR display EOTF to an appropriateEOTF (S203).

In view of step S201 to step S203, while the display settings are set(S105), the EOTF set to the SDR display is set to a recommended EOTFcorresponding to the obtained setting information. Further, thus, instep S106 performed after step S105, it is possible to determine an SDRluminance value by using the recommended EOTF.

When determining that the system side cannot switch the SDR display EOTF(No in S202), display setting unit 201 displays on the screen a messagewhich encourages the user to change the EOTF by a manual operation(S204). For example, display setting unit 201 displays on a screen amessage such as “Please set a display gamma to 2.4”. That is, while thedisplay settings are set (S105), when it is not possible to switch theEOTF set to the SDR display, display setting unit 201 displays on theSDR display a message which encourages the user to switch to arecommended EOTF an EOTF (SDR display EOTF) set to the SDR display.

Next, the SDR display displays a pseudo HDR video image (SDR signal),yet determines whether or not a display parameter of the SDR displaymatches setting information by using the setting information beforedisplaying the pseudo HDR video image (S205).

When determining that the display parameter set to the SDR display isdifferent from the setting information (Yes in S205), display settingunit 201 determines whether or not it is possible to switch the displayparameter of the SDR display (S206).

When determining that it is possible to switch the display parameter ofthe SDR display (Yes in S206), display setting unit 201 switches thedisplay parameter of the SDR display according to the settinginformation (S207).

In view of step S204 to step S207, while the display settings are set(S105), the display parameter set to the SDR display is set to arecommended display parameter corresponding to the obtained settinginformation.

When determining that the system side cannot switch the displayparameter (No in S206), display setting unit 201 displays on the screena message which encourages the user to change the display parameter setto the SDR display by a manual operation (S208). For example, displaysetting unit 201 displays on the screen a message such as “Please set adisplay mode to a dynamic mode and maximize a backlight”. That is,during the setting (S105), when it is not possible to switch the displayparameter set to the SDR display, display setting unit 201 displays onthe SDR display a message which encourages the user to switch to arecommended display parameter a display parameter set to the SDRdisplay.

41. Modified Example 1

As described above, the exemplary embodiment has been described as anexemplary technique disclosed in this application. However, thetechnique according to the present disclosure is not limited to this,and is applicable to a first exemplary embodiment, too, for whichchanges, replacement, addition and omission have been optionally carriedout. Further, it is also possible to provide new exemplary embodimentsby combining each component described in the above exemplary embodiment.

Hereinafter, another exemplary embodiment will be described.

An HDR video image is, for example, a video image in a Blu-ray Disc, aDVD, a video distribution website on the Internet, a broadcast and aHDD.

Converting device 100 (HDR→pseudo HDR conversion processor) may beprovided in a disk player, a disk recorder, a set-top box, a television,a personal computer or a smartphone. Converting device 100 may beprovided in a server device on the Internet.

Display device 200 (SDR display) is, for example, a television, apersonal computer and a smartphone.

Display characteristics information obtained by converting device 100may be obtained from display device 200 via a HDMI (registeredtrademark) cable or a LAN cable by using HDMI (registered trademark) oranother communication protocol. As the display characteristicsinformation obtained by converting device 100, display characteristicsinformation included in model information of display device 200 may beobtained via the Internet. Further, the user may perform a manualoperation to set the display characteristics information to convertingdevice 100. Furthermore, the display characteristics information may beobtained by converting device 100 immediately before generation of apseudo HDR video image (steps S101 to S104) or at a timing at whichdefault settings of a device are made or at which a display isconnected. For example, the display characteristics information may beobtained immediately before conversion into a display luminance value orat a timing at which converting device 100 is connected to displaydevice 200 for the first time by a HDMI (registered trademark) cable.

Further, a CPL and a CAL of an HDR video image may be provided percontent or may be provided per scene. That is, according to theconverting method, luminance information (a CPL and a CAL) whichcorresponds to each of a plurality of scenes of a video image, and whichincludes per scene at least one of a first maximum luminance value whichis a maximum value among luminance values for a plurality of imagesconfiguring each scene, and an average luminance value which is anaverage of luminance values for a plurality of images configuring eachscene may be obtained. According to first luminance conversion, for eachof a plurality of scenes, a display luminance value may be determinedaccording to luminance information corresponding to each scene.

Further, the CPL and the CAL may be packaged in the same medium (aBlu-ray Disc, a DVD or the like) as that of HDR video images or may beobtained from a location different from HDR video images, for example,by converting device 100 from the Internet. That is, luminanceinformation including at least one of the CPL and the CAL may beobtained as meta information of a video image, or may be obtained via anetwork.

Further, during first luminance conversion (HPL DPL) of convertingdevice 100, a fixed value may be used without using a CPL, a CAL and adisplay peak luminance (DPL). Furthermore, this fixed value may bechanged from an outside. Still further, a CPL, a CAL and a DPL may beswitched between a plurality of types. For example, the DPL may beswitched between only three types of 200 nit, 400 nit and 800 nit, ormay take a value which is the closest to display characteristicsinformation.

Further, an HDR EOTF may not be SMPTE 2084, and another type of an HDREOTF may be used. Furthermore, a maximum luminance (HPL) of an HDR videoimage may not be 10,000 nit and may be, for example, 4,000 nit or 1,000nit.

Still further, bit widths of code values may be, for example, 16, 14,12, 10 and 8 bits.

Moreover, SDR inverse EOTF conversion is determined based on displaycharacteristics information yet a fixed conversion function (which canbe changed from an outside, too) may be used. For the SDR inverse EOTFconversion, a function defined by, for example, Rec. ITU-R BT.1886 maybe used. Further, types of SDR inverse EOTF conversion may be narroweddown to several types, and a type which is the closest to input/outputcharacteristics of display device 200 may be selected and used.

Furthermore, a fixed mode may be used for a display mode, and thedisplay mode may not be included in display characteristics information.

Still further, converting device 100 may not transmit settinginformation, and display device 200 may adopt fixed display settings andmay not change the display settings. In this case, display setting unit201 is unnecessary. Further, setting information may be flag informationindicating a pseudo HDR video image or a non-pseudo HDR video image, andmay be, for example, changed to settings for displaying the pseudo HDRvideo image the most brightly in case of the pseudo HDR video image.That is, while the display settings are set (S105), when the obtainedsetting information indicates a signal indicating a pseudo HDR videoimage converted by using a DPL, brightness settings of display device200 may be switched to settings for displaying the pseudo HDR videoimage the most brightly.

42. Modified Example 2

Further, in the first luminance conversion (HPL DPL) of convertingdevice 100, conversion is performed according to, for example, afollowing equation.

In this regard, L represents a luminance value normalized to 0 to 1, andS1, S2, a, b and M are values set based on a CAL, a CPL and a DPL. Inrepresents a natural logarithm. V represents a converted luminance valuenormalized to 0 to 1. As in an example in FIG. 39A, when the CAL is 300nit, the CPL is 2,000 nit, the DPL is 750 nit, conversion is notperformed up to CAL+50 nit and conversion is performed in case of 350nit or more, respective values take, for example, following values.

S1=350/10000

S2=2000/10000

M=750/10000

a=0.023

b=S1−a*ln(S1)=0.112105

That is, according to the first luminance conversion, when an SDRluminance value is between an average luminance value (CAL) and a firstmaximum luminance value (CPL), a display luminance value correspondingto an HDR luminance value is determined by using a natural logarithm.

40. Effect and Others

By converting each HDR video image by using information such as acontent peak luminance or a content average luminance of each HDR videoimage, it is possible to change a converting method according to contentand convert each HDR video image while keeping an HDR gradation as muchas possible. Further, it is possible to suppress a negative influencethat each HDR video image is too dark or too bright. More specifically,by mapping a content peak luminance of each HDR video image on a displaypeak luminance, a gradation is kept as much as possible. Further, eachpixel value equal to or less than an average luminance is not changed toprevent an overall brightness from changing.

Furthermore, by converting each HDR video image by using a peakluminance value and a display mode of an SDR display, it is possible tochange a converting method according to display environment of the SDRdisplay, and display each video image (pseudo HDR video image) havingHDR quality at the same gradation or brightness as that of an originalHDR video image according to capability of the SDR display. Morespecifically, a display peak luminance is determined based on a maximumluminance and a display mode of the SDR display, and each HDR videoimage is converted so as not to exceed the peak luminance value.Consequently, each HDR video image is displayed without substantiallydecreasing a gradation of each HDR video image up to a brightness whichthe SDR display can display, and a luminance value of a brightness whichcannot be displayed is lowered to a brightness which can be displayed.

As described above, it is possible to reduce information of a brightnesswhich can be displayed, and display each video image having qualityclose to an original HDR video image without decreasing a gradation of abrightness which can be displayed. For example, for a display whose peakluminance is 1,000 nit, each HDR video image is converted into a pseudoHDR video image whose peak luminance is suppressed to 1,000 nit to keepan overall brightness, and a luminance value changes according to adisplay mode of the display. Hence, a luminance converting method ischanged according to the display mode of the display. If a luminancehigher than the peak luminance of the display is permitted for a pseudoHDR video image, there is a case where the high luminance is replacedwith a peak luminance of the display side and is displayed. In thiscase, the pseudo HDR video image becomes entirely darker than anoriginal HDR video image. By contrast with this, when a luminance lowerthan the peak luminance of the display is converted as a maximumluminance, this low luminance is replaced with the peak luminance of thedisplay side. Therefore, the pseudo HDR video image becomes entirelybrighter than an original HDR video image. Moreover, the luminance islower than the peak luminance of the display side, and thereforecapability related to a display gradation is not used at maximum.

Further, the display side can display each pseudo HDR video image betterby switching display settings by using setting information. When, forexample, a brightness is set dark, a high luminance cannot be displayed,and therefore HDR quality is undermined. In this case, the displaysettings are changed or a message which encourages a change of thedisplay settings is displayed to exhibit display capability and displayhigh gradation video images.

OVERALL CONCLUSION

The playback method and the playback device according to one or aplurality of aspects of the present disclosure have been described basedon the exemplary embodiment. However, the present disclosure is notlimited to this exemplary embodiment. The scope of one or a plurality ofexemplary embodiments of the present disclosure may include exemplaryembodiments obtained by applying, to the present exemplary embodiment,various deformations one of ordinary skill in the art conceives, andexemplary embodiments obtained by combining the components according todifferent exemplary embodiments without departing from the spirit of thepresent disclosure.

In the above exemplary embodiment, each component may be configured bydedicated hardware such as a circuit or may be realized by executing asoftware program suitable to each component. Each component may berealized by causing a program executing unit such as a CPU or aprocessor to read a software program recorded on a recording medium suchas a hard disk or a semiconductor memory and execute the softwareprogram.

The present disclosure is applicable to content data generating devices,video stream transmitting devices such as Blu-ray devices or videodisplay devices such as televisions.

What is claimed is:
 1. A method used by a playback device, comprising:when a version of a transmission protocol is a first version, thetransmission protocol being used to transmit a signal between theplayback device and a display device, transmitting first meta data tothe display device, the first meta data including information that iscommonly used for a plurality of images included in a continuousplayback unit of a first video signal and relates to a luminance rangeof the first video signal, without transmitting second meta data to thedisplay device, the second meta data including information that iscommonly used for a unit subdivided compared to the continuous playbackunit of the first video signal and relates to the luminance range of thefirst video signal; and when the version of the transmission protocol isa second version, transmitting the first meta data and the second metadata to the display device.
 2. The method according to claim 1, furthercomprising, when the version of the transmission protocol is the firstversion, performing a conversion process of converting the luminancerange of the first video signal by using the second meta data to obtaina second video signal, and transmitting the second video signal to thedisplay device.
 3. The method according to claim 1, further comprising:when the version of the transmission protocol is the second version, andthe display device does not include capability of performing aconversion process of converting the luminance range of the first videosignal by using the second meta data, performing the conversion processto obtain a second video signal and transmitting the second video signalto the display device; and when the version of the transmission protocolis the second version and the display device includes capability ofperforming the conversion process, transmitting the first video signalto the display device without performing the conversion process.
 4. Themethod according to claim 1, wherein, when the playback device does notinclude capability of a conversion process of converting the luminancerange of the first video signal by using the second meta data, thesecond meta data is not transmitted to the display device withoutperforming the conversion process.
 5. The method according to claim 1,wherein a luminance value of the first video signal is encoded as a codevalue, and the first meta data includes information for specifying anEOTF (Electro-Optical Transfer Function) of associating a plurality ofluminance values and a plurality of code values.
 6. The method accordingto claim 1, wherein the second meta data indicates masteringcharacteristics of the first video signal.
 7. A playback method forplaying back a video signal, a luminance of the video signal being afirst luminance value in a first luminance range whose maximum luminancevalue is defined as a first maximum luminance value exceeding 100 nit,the playback method comprising: determining whether or not aninter-screen change amount of a luminance value of the video signalexceeds a predetermined first threshold; and adjusting the luminancevalue of the video signal when it is determined that the change amountexceeds the first threshold.
 8. The playback method according to claim7, wherein the adjustment includes adjusting, for a pixel whose changeamount exceeds the first threshold, a luminance value of the pixel suchthat the change amount of the pixel is the first threshold or less. 9.The playback method according to claim 7, wherein the determinationincludes determining whether or not a difference exceeds the firstthreshold, the difference being a difference between a peak luminance ofa first image included in the video signal, and each of luminance valuesof a plurality of pixels included in the video signal and included in asecond image subsequent to the first image, and the adjustment includesadjusting, for a pixel the difference of which exceeds the firstthreshold, a luminance value of the pixel such that the difference ofthe pixel is the first threshold or less.
 10. The playback methodaccording to claim 7, wherein the determination includes determiningwhether or not the change amount of the luminance value at a referencetime interval exceeds the first threshold, the reference time intervalbeing an integer multiple of a reciprocal of a frame rate of the videosignal.
 11. The playback method according to claim 7, wherein thedetermination includes determining whether or not a rate of pixels thechange amounts of which exceed the first threshold with respect to aplurality of pixels exceeds a second threshold, the plurality of pixelsbeing included in an image included in the video signal, and theadjustment includes adjusting, when the rate exceeds the secondthreshold, the luminance values of a plurality of pixels such that therate is the second threshold or less.
 12. The playback method accordingto claim 7, wherein the determination includes determining, for each ofa plurality of areas obtained by dividing a screen, whether or not theinter-screen change amount of the luminance value of each of a pluralityof areas exceeds the first threshold, and the adjustment includesperforming, an adjustment process of lowering a luminance value of anarea for which it is determined that the change amount exceeds the firstthreshold.
 13. A playback method for playing back a video signal, aluminance of the video signal being a first luminance value in a firstluminance range whose maximum luminance value is defined as a firstmaximum luminance value exceeding 100 nit, the playback methodcomprising: determining whether or not a luminance value of an image ofthe video signal exceeds a predetermined first threshold; and adjustingthe luminance value of the image when it is determined that theluminance value exceeds the first threshold.
 14. The playback methodaccording to claim 13, wherein the determination includes determining anumber of pixels whose luminance values exceed the first threshold withrespect to a plurality of pixels included in the image, and theadjustment includes lowering, when the number of pixels exceeds a thirdthresholds, the luminance value of the image such that the number ofpixels is the third threshold or less.
 15. The playback method accordingto claim 13, wherein the determination includes determining, a rate ofpixels whose luminance values exceed the first threshold with respect toa plurality of pixels included in the image, and the adjustment includeslowering, when the rate exceeds a third threshold, the luminance valueof the image such that the rate is the third threshold or less.
 16. Theplayback method according to claim 13, wherein the first threshold is avalue calculated based on an upper limit value of a voltage which issimultaneously applicable to a plurality of pixels in a display devicethat displays the video signal.
 17. A playback device comprising one ormore memories and circuitry which, in operation: transmits, when aversion of a transmission protocol is a first version, first meta datato a display device without transmitting second meta data to the displaydevice, the transmission protocol being used to transmit a signalbetween the playback device and the display device, the first meta dataincluding information that is commonly used for a plurality of imagesincluded in a continuous playback unit of a first video signal andrelates to a luminance range of the first video signal, the second metadata including information that is commonly used for a unit subdividedcompared to the continuous playback unit of the first video signal andrelates to the luminance range of the first video signal; and transmits,when the version of the transmission protocol is a second version, thefirst meta data and the second meta data to the display device.
 18. Aplayback device that plays back a video signal, a luminance of the videosignal being a first luminance value in a first luminance range whosemaximum luminance value is defined as a first maximum luminance valueexceeding 100 nit, the playback device comprising one or more memoriesand circuitry which, in operation: determines whether or not aninter-screen change amount of a luminance value of the video signalexceeds a predetermined first threshold; and adjusts the luminance valueof the video signal when it is determined that the change amount exceedsthe first threshold.
 19. A playback device that plays back a videosignal, wherein a luminance of the video signal is a first luminancevalue in a first luminance range whose maximum luminance value isdefined as a first maximum luminance value exceeding 100 nit, and theplayback device comprises one or more memories and circuitry which, inoperation, and the playback device determines whether or not a luminancevalue of an image included in the video signal exceeds a predeterminedfirst threshold, and adjusts the luminance value of the image when it isdetermined that the luminance value exceeds the first threshold.